CN114341310A

CN114341310A - Heat conducting sheet and method for producing same

Info

Publication number: CN114341310A
Application number: CN202080055463.1A
Authority: CN
Inventors: 外谷荣一; 松井孝二; 丰川裕也; 柴田和希; 香川胜彦; 山口隆幸
Original assignee: Showa Pill Tube Co ltd
Current assignee: Showa Pill Tube Co ltd
Priority date: 2019-07-31
Filing date: 2020-06-25
Publication date: 2022-04-12
Also published as: TW202113027A; KR20220042142A; US20220276011A1; WO2021019982A1; JPWO2021019982A1

Abstract

The invention provides a heat conductive sheet and the like having excellent heat conductivity in the thickness direction and excellent flexibility. The thermally conductive sheet 100 includes: a plurality of heat conduction portions 10 provided continuously from one main surface to the other main surface, respectively; and a joining portion 20 that joins adjacent interfaces of the plurality of heat conductive portions 10 stacked in the main surface direction to each other, the heat conductive sheet 100 being a sheet as a whole, wherein the heat conductive portion 10 includes a void portion, the joining portion 20 is made of a material including a flexible resin material, and a void layer is locally formed, and a part of the resin material partially penetrates into the void portion of the heat conductive portion 10. According to the above configuration, the flexibility of the thermally conductive sheet 100 is improved by the void portions of the thermally conductive portion 10 and the void layers of the joining portion 20, and the resin material is made to penetrate into a part of the void portions of the thermally conductive portion 10, whereby the strength of joining the thermally conductive portions 10 to each other can be secured while forming the void layers between the thermally conductive portions 10.

Description

Heat conducting sheet and method for producing same

Technical Field

The present invention relates to a heat conductive sheet and a method for manufacturing the same.

Background

In recent years, heat dissipation of heat generating components such as electronic devices, vehicle headlights, and vehicle-mounted batteries has become an urgent issue. For example, the amount of heat generated tends to increase due to miniaturization and high integration of electronic components such as a Central Processing Unit (CPU) of a computer, a Graphic Processing Unit (GPU), SoC (System on Chip) of a smart phone, a DSP (Digital Signal Processor) and a microcomputer of a built-in device, a semiconductor device such as a transistor, a Light Emitting Diode (LED), a light emitting body such as Electroluminescence (EL), and a liquid crystal. The life reduction and malfunction of the devices and systems caused by the heat generation of these electronic components are becoming problems, and the demand for measures against heat dissipation of the electronic components has been increasing year by year.

As a heat radiation countermeasure against such a heat generating element, in addition to forced cooling by an air cooling fan, a heat radiation member such as a metal heat radiation fin or a peltier element is used. In such a heat radiating member, grease has been conventionally applied to a surface thermally connected to a heat generating element to prevent an air layer serving as a heat insulating layer from being formed at the interface. However, the thermal conductivity of ordinary grease is not high. Therefore, a diamond grease in which diamond having a relatively high thermal conductivity is dispersed may be used (for example, see patent document 1).

However, diamond grease is expensive. In addition, it is also difficult to obtain sufficient thermal conductivity when diamond grease is used.

Documents of the prior art

Patent document

Patent document 1: japanese Kohyo publication No. 2017-530220

Disclosure of Invention

An object of the present invention is to provide a thermally conductive sheet having excellent thermal conductivity in the thickness direction and excellent flexibility, and a method for producing the thermally conductive sheet.

The thermally conductive sheet according to claim 1 of the present invention includes: a plurality of heat conduction portions that are respectively provided continuously from one main surface to the other main surface; and a joining portion that joins adjacent interfaces of the plurality of heat-conducting portions stacked in the main surface direction to each other, the heat-conducting sheet being a sheet as a whole, the heat-conducting portion including a void portion, the joining portion being made of a material including a flexible resin material and having a void layer formed locally, and a part of the resin material being capable of penetrating locally into the void portion of the heat-conducting portion. According to the above configuration, the flexibility and the pliability of the thermally conductive sheet are improved by the void portions of the thermally conductive portions and the void layers of the joining portions, and the void layers are formed between the thermally conductive portions by the resin material penetrating into a part of the void portions of the thermally conductive portions, and the strength of joining the thermally conductive portions to each other is ensured.

Further, according to the thermally conductive sheet of the 2 nd aspect of the invention, in addition to the above constitution, in the thickness direction of the thermally conductive sheet0.2N/mm²When the thermally conductive sheet is pressed by surface pressure, the thermal conductivity in the thickness direction of the thermally conductive sheet is defined as lambda_0.2[W/m·K]0.8N/mm in the thickness direction of the heat-conducting sheet²When the thermally conductive sheet is pressed by surface pressure, the thermal conductivity in the thickness direction of the thermally conductive sheet is defined as lambda_0.8[W/m·K]At this time, λ of 1.5. ltoreq_0.8/λ_0.2A relation less than or equal to 3.5.

Further, according to the thermally conductive sheet of claim 3, in addition to any of the above configurations, a ratio of the void layer in the joining portion may be 2% by volume or more and 30% by volume or less.

In addition, according to the thermally conductive sheet of claim 4 of the present invention, in addition to any one of the above configurations, the thermally conductive portion may be formed of a material containing graphite in a flake form and resin fibers.

In addition, according to the thermally conductive sheet of the 5 th aspect of the present invention, in addition to any one of the above configurations, the resin fiber may be an aromatic polyamide fiber.

In addition to the above configuration, the thermally conductive sheet according to claim 6 of the present invention may be configured such that the graphite is expanded graphite.

In addition to any one of the above configurations, the thermally conductive sheet according to claim 7 of the present invention may have a thermal conductivity in a thickness direction of the thermally conductive sheet measured by a laser flash method on the main surface of the thermally conductive sheet of 10W/m · K or more and 200W/m · K or less.

In addition, according to the thermally conductive sheet of the 8 th aspect of the present invention, in addition to any of the above configurations, a width of the thermally conductive portion in an in-plane direction of the thermally conductive sheet may be 50 μm or more and 300 μm or less.

In addition, according to the thermally conductive sheet of the 9 th aspect of the present invention, in addition to any of the above configurations, the thickness of the thermally conductive sheet may be 0.2mm or more and 5mm or less.

Further, according to the thermally conductive sheet of the 10 th aspect of the present invention, in addition to any one of the above configurations, the thickness direction of the thermally conductive sheet is set to 0.2N/mm²The thickness of the thermally conductive sheet may be 0.1mm to 5mm when the thermally conductive sheet is pressed by the surface pressure of (2).

In addition, according to the thermally conductive sheet of the 11 th aspect of the present invention, in addition to any of the above configurations, the thermally conductive sheet may have a surface roughness Ra of 0.1 μm or more and 100 μm or less.

Further, according to the thermally conductive sheet of the 12 th aspect of the present invention, in addition to any one of the above configurations, the resin material may include: a polyrotaxane having a cyclic molecule, a first polymer, and a capping group; and a second polymer in which the polyrotaxane and the second polymer are bonded via the cyclic molecule, wherein the first polymer has a linear molecular structure and includes the cyclic molecule in a puncture-like manner, and the blocking group is provided in the vicinity of both ends of the first polymer.

In addition, according to the thermally conductive sheet of claim 13 of the present invention, in addition to any one of the above configurations, an angle formed by a normal line of the thermally conductive sheet and a normal line of the thermally conductive portion may be 25 ° or more and 90 ° or less.

In addition, according to the thermally conductive sheet of claim 14 of the present invention, in addition to any one of the above configurations, an interface between the thermally conductive portion and the joining portion may be formed in a curved surface shape. According to the above configuration, when the heat conductive sheet is pressed in the thickness direction, the heat conductive portion and the joining portion are laminated in a curved shape, so that the heat conductive sheet is more easily deformed, and for example, the heat conductive sheet is easily brought into close contact with the heat generating element without forming a gap when the heat conductive sheet is in surface contact with the heat generating element, whereby the heat conductivity can be improved.

In addition, according to the thermally conductive sheet of the 15 th aspect of the present invention, in addition to any one of the above configurations, the thicknesses of the thermally conductive portion and the joining portion which are laminated with each other may be locally different in the main surface direction of the thermally conductive sheet.

In addition, a method of manufacturing a thermally conductive sheet according to the 16 th aspect of the present invention is a method of manufacturing a thermally conductive sheet in which a plurality of thermally conductive portions each provided continuously from one main surface to the other main surface are laminated in a main surface direction, and may include: impregnating a heat-conductive-portion-forming sheet constituting a heat conductive portion with an uncured resin material; a step of winding the heat-conductive-portion-forming sheet impregnated with an uncured resin material into a roll shape; curing the uncured resin material in the state of the wound body; and cutting the wound body in which the resin material is cured on a plane perpendicular to, parallel to, or inclined to the axial direction of the roll shape. Accordingly, the laminated state can be easily obtained by winding the resin material-impregnated heat conduction portion forming sheet into a roll shape. Further, by forming the wound body, the subsequent processing and cutting can be easily performed, and the thermally conductive sheet can be obtained at low cost.

In addition, according to the method for producing a thermally conductive sheet of the 16 th aspect of the present invention, in addition to the above, before the step of impregnating the sheet for forming a thermally conductive portion with an uncured resin material, a step of preparing the sheet for forming a thermally conductive portion in the form of a roll-shaped wound body may be further included. Accordingly, the following advantages are obtained: by impregnating a resin material into a heat-conducting portion-forming sheet prepared in advance in a roll shape and then winding the sheet to another roll, it is possible to prepare a long heat-conducting portion-forming sheet and to impregnate the sheet with the resin material with a space-saving and highly efficient manner.

Further, according to the method for producing a thermally conductive sheet of the 17 th aspect of the present invention, in addition to any one of the above, the uncured resin material may be a thermosetting resin. Accordingly, the following advantages are obtained: even in a state where the resin material of the thermosetting resin is impregnated into the wound body, the resin material can be easily cured by heating, and the production efficiency can be improved.

Drawings

Fig. 1 is a schematic cross-sectional view showing a heat sink using a thermally conductive sheet according to embodiment 1 of the present invention.

Fig. 2 is a schematic plan view with a partially enlarged view showing a thermally conductive sheet according to embodiment 1 of the present invention.

Fig. 3 is a schematic perspective view with a partially enlarged view showing a thermally conductive sheet according to embodiment 1 of the present invention.

Fig. 4 is a schematic side view showing a thermally conductive sheet according to embodiment 1 of the present invention.

In fig. 5, fig. 5A and 5B are conceptual views of an example of the resin material constituting the joint portion.

Fig. 6 is a schematic perspective view with a partially enlarged view showing a thermally conductive sheet according to embodiment 2.

Fig. 7 is a schematic side view showing a heat conductive sheet according to embodiment 2.

Fig. 8 is a schematic plan view showing a heat conductive sheet according to embodiment 3.

Fig. 9A to 9C are schematic cross-sectional views showing a method for producing a thermally conductive sheet according to embodiment 1.

Fig. 10 is a schematic cross-sectional view showing another example of the step of stacking the thermally conductive sheets according to embodiment 1.

Fig. 11 is a schematic cross-sectional view showing another example of the step of stacking the thermally conductive sheets according to embodiment 1.

Fig. 12A to 12D are schematic cross-sectional views showing a method for producing a thermally conductive sheet according to embodiment 2.

Fig. 13A to 13B are vertical sectional views schematically showing changes in the thickness of the thermally conductive sheet and changes in the inclination of the thermally conductive portion before and after the step of pressing the thermally conductive sheet according to embodiment 2.

Fig. 14A to 14D are schematic cross-sectional views showing a method for producing a thermally conductive sheet according to embodiment 3.

Fig. 15 is a schematic view showing a method for producing a thermally conductive sheet according to embodiment 4.

Fig. 16 is a schematic cross-sectional view showing a state in which the resin material of the roll of fig. 15 is cured.

Fig. 17 is a schematic perspective view showing a cutting position of the laminate.

Fig. 18 is a schematic perspective view showing another example of the cutting position of the laminate.

Fig. 19A to 19C are schematic cross-sectional views showing another example of the cutting position of the laminate.

Fig. 20 is an enlarged sectional photograph of the thermally conductive sheet of example 4.

Fig. 21 is an enlarged sectional photograph of the thermally conductive sheet of example 1.

Fig. 22 is an enlarged sectional photograph of a main portion of fig. 23.

Fig. 23 is an enlarged sectional photograph of a main portion of the thermally conductive sheet of example 1.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below are examples for embodying the technical idea of the present invention, and the present invention is not limited to the following. In addition, the components shown in the claims are not necessarily specified as the components of the embodiments in the present specification. In particular, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are merely illustrative examples, and the scope of the present invention is not intended to be limited thereto unless otherwise specified. The sizes, positional relationships, and the like of the components shown in the drawings may be exaggerated for clarity of description. In the following description, the same names and symbols denote the same or homogeneous members, and detailed description thereof will be omitted as appropriate. Further, each element constituting the present invention may be configured such that a plurality of elements are constituted by the same member and one member doubles as a plurality of elements, or conversely, the function of one member may be shared by a plurality of members.

[ embodiment 1]

The heat conductive sheet can be used as a heat radiating member of various heating elements. The heat-generating body can be preferably exemplified by: CPU or GPU, DSP, microcomputer and other operation elements; a driving element such as a transistor; light Emitting elements such as an LED, an O-LED (Organic Light Emitting Diode), and a liquid crystal; light sources such as halogen lamps; the motor and the like drive parts and the like. Here, as embodiment 1, an example in which a heat sink is applied to a CPU will be described. Here, as shown in the schematic cross-sectional view of fig. 1, a heat sink 1000 is configured in which a heat conductive sheet 100 is thermally connected between a CPU as a heat generating body HG and a cooling fin as a heat sink HS.

(Heat-conducting sheet 100)

First, the thermally conductive sheet 100 according to embodiment 1 will be described with reference to fig. 2 to 4. In these drawings, fig. 2 is a schematic plan view showing the thermally conductive sheet 100 according to embodiment 1, fig. 3 is a schematic perspective view showing the thermally conductive sheet 100, fig. 4 is a schematic side view showing the thermally conductive sheet 100, and fig. 5 is a conceptual view showing an example of a resin material constituting a joint portion.

As shown in fig. 2 to 4, the thermally conductive sheet 100 of embodiment 1 includes a plurality of thermally conductive portions 10 in a layer shape and a joining portion 20 joining the respective thermally conductive portions 10, and is in a sheet shape as a whole. The heat conductive portion 10 is made of a material including graphite in a scaly form (scaly graphite) 11 and resin fibers 12, and is provided from one main surface to the other main surface of the heat conductive sheet 100, in other words, the heat conductive portion 10 is exposed at both main surfaces of the heat conductive sheet 100. The joining portion 20 is made of a flexible resin material, and the graphite 11 is oriented so that the thickness direction thereof is along the direction of the thickness T10 of the layered heat conductive portion 10. In the thermally conductive sheet 100 of the present embodiment, an angle θ 1 formed by the normal N100 of the thermally conductive sheet 100 and the normal N10 of the thermally conductive portion 10 is 25 ° or more and 90 ° or less.

In other words, when axes intersecting each other in the plane direction of the thermally conductive sheet 100 are defined as an x axis and a y axis, and an axis intersecting the x axis and the y axis is defined as a z axis, the thermally conductive sheet 100 includes: a plurality of heat conduction portions 10 extending in the x-axis direction; and a joining portion 20 made of a flexible resin material and joining the heat-conducting portions 10 in the y-axis direction. The heat conduction portion 10 is made of a material including a plurality of graphite particles (flake graphite particles) 11 in a flake shape and resin fibers 12. In the heat conductive portion 10, the graphite (flake graphite) 11 is oriented such that the thickness direction thereof is along the y-axis direction.

In other words, the heat conductive sheet 100 of the present embodiment includes: a plurality of heat conduction portions 10 that preferentially transfer heat in a 1 st direction, which is a direction of thickness T100 of the heat conduction sheet 100, and extend in a 2 nd direction intersecting the 1 st direction; and a joining portion 20 made of a flexible resin material and joining the heat-conducting portions 10 in a 3 rd direction intersecting the 1 st direction and the 2 nd direction, the heat-conducting portions 10 being made of a material including graphite 11 having a scaly shape and an orientation such that a thickness direction thereof is along the 3 rd direction and resin fibers 12.

According to such a configuration, the thermally conductive sheet 100 has high thermal conductivity in the thickness direction with respect to a predetermined direction in the plane of the thermally conductive sheet 100 in the form of a sheet, in other words, the thermal conductivity in the z-axis direction is higher than that in the y-axis direction, and heat can be transmitted preferentially in the z-axis direction (that is, the thickness direction of the thermally conductive sheet 100), so that the thermally conductive sheet 100 as a whole can have excellent thermal conductivity in the thickness direction and excellent flexibility. As a result, the surface shape of the heating element HG can be preferably followed, and heat conduction and heat dissipation can be preferably performed. More specifically, the adhesion to the heating element HG is improved, and the reduction in thermal conductivity due to the air layer remaining between the thermally conductive sheet 100 and the heating element HG can be effectively prevented. In particular, since the thermally conductive sheet 100 is excellent in thermal conductivity in the thickness direction, the area in contact with the heating element HG can be increased, and the overall thermal conductivity and heat dissipation can be improved. Even if the heating element HG has a complicated shape or has a large surface irregularity, it can follow the surface shape of the member well, and the above-described functions can be effectively exhibited.

The reason why such an excellent effect is obtained is considered as follows. That is, the heat conducting portion 10 contains the flake graphite 11 as a material having high heat conductivity, the flake graphite 11 is oriented in a predetermined direction in the heat conducting portion 10, and the heat conducting portion 10 is continuously provided from one main surface to the other main surface of the heat conducting sheet 100, whereby the distance between the flake graphite 11 in the thickness direction of the heat conducting sheet 100 can be shortened without making the content of the flake graphite 11 extremely high, and the ratio of the flake graphite 11 in contact with each other can be effectively increased. As a result, sufficient flexibility can be ensured, and the thermal conductivity in the thickness direction is particularly excellent.

In addition, by providing the joining portion 20 made of a resin material having flexibility in addition to the heat conductive portion 10, the heat conductive sheet 100 can be made particularly excellent in flexibility. Further, since the thermally conductive sheet 100 is excellent in flexibility, the following property to the surface shape of the heating element HG is improved, and even if the member has a complicated shape or has relatively large irregularities on the surface, it is possible to effectively prevent an unexpected gap from being generated between the thermally conductive sheet 100 and the member. As a result, heat dissipation and the like of the above-described components can be performed preferably.

Further, since the heat conductive portion 10 includes the resin fibers in addition to the flake graphite 11, even when the content of the flake graphite 11 in the heat conductive portion 10 is relatively high, the flake graphite 11 can be preferably held in the heat conductive portion 10, and the flexibility of the heat conductive portion 10 and the flexibility of the entire heat conductive sheet 100 can be made high.

On the other hand, if the conditions described above are not satisfied, satisfactory results cannot be obtained. For example, in a sheet that is configured only by portions corresponding to the heat-conductive portions and does not have portions corresponding to the joining portions, the flexibility of the entire sheet is insufficient, and sufficient heat conductivity cannot be exhibited depending on the shape of a member to which the sheet is applied. In addition, in the sheet that is configured only by the portions corresponding to the joining portions and does not have the portions corresponding to the heat-conductive portions, the heat conductivity is low. Further, when the heat conductive portion does not contain resin fibers, it becomes difficult to sufficiently improve flexibility of the entire sheet, for example. In addition, in the case where a dense resin layer is formed of a molten resin, or the like in the heat conductive portion instead of the resin fibers, it becomes difficult to sufficiently improve flexibility of the entire sheet, for example. In addition, when the heat conductive portion does not contain graphite, the heat conductivity becomes low. In addition, when the graphite (flake graphite) in the heat conductive portion has an orientation other than the above-described orientation or does not have an orientation, it becomes difficult to sufficiently obtain excellent heat conductivity in the thickness direction of the sheet. Even if the heat conductive portion is made of a material including graphite in a flake shape and resin fibers, when the heat conductive portion is not provided from one main surface to the other main surface of the heat conductive sheet, for example, when the heat conductive portion is exposed only on one surface or when both surfaces are not exposed, heat dissipation from a member in contact with the heat conductive sheet is insufficient when the heat conductive sheet is used. In addition, when ordinary graphite particles (substantially spherical, irregular particles, etc.) are used instead of scaly graphite (scaly graphite), it is also difficult to sufficiently obtain excellent thermal conductivity in the thickness direction of the sheet. If the angle θ 1 formed by the normal line of the thermally conductive sheet and the normal line of the thermally conductive portion is less than the lower limit value, heat transfer in the thickness direction of the thermally conductive sheet becomes insufficient, and heat dissipation from a member in contact with the thermally conductive sheet becomes insufficient when the thermally conductive sheet is used.

In the heat conduction portion 10, a large amount of the plurality of flaky graphite 11 included in the heat conduction portion 10 may be oriented as described above, and all of the flaky graphite 11 may not be oriented so that the thickness direction of the flaky graphite 11 is along the thickness direction of the layered heat conduction portion 10 (particularly, the y-axis direction in the configuration shown in fig. 3 and 4). In such a case, the above-described effects are also sufficiently exhibited.

The ratio of the flaky graphite 11 exhibiting the above orientation among the flaky graphite 11 contained in the heat conductive portion 10 is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more by number.

The above orientation does not mean that the thickness direction (normal direction) of the flake graphite particles 11 completely coincides with the thickness direction of the layered heat conduction part 10 (particularly, the y-axis direction in the structure shown in fig. 3 and 4), and for example, the angle θ formed between the thickness direction (normal direction) of the flake graphite particles 11 and the thickness direction of the layered heat conduction part 10 may be 20 ° or less, and particularly, preferably 10 ° or less.

As described above, the angle θ 1 formed between the normal N100 of the thermally conductive sheet 100 and the normal N10 of the thermally conductive portion 10 may be 25 ° or more and 90 ° or less, preferably 30 ° or more and 90 ° or less, more preferably 35 ° or more and 90 ° or less, and still more preferably 40 ° or more and 90 ° or less. Accordingly, the above effects are more remarkably exhibited.

(Heat conduction part)

The heat conductive sheet 100 includes a plurality of heat conductive portions 10 provided from one main surface to the other main surface of the heat conductive sheet. In the present embodiment, each heat conduction portion 10 extends in the x-axis direction in a plan view of the heat conduction sheet 100. The heat conduction portion 10 is a main portion contributing to the heat conductivity of the entire heat conduction sheet 100 (particularly, the heat conductivity in the thickness direction (z-axis direction) of the heat conduction sheet 100).

The heat conducting portion 10 includes a plurality of flaky graphite (flaky graphite) 11 and resin fibers 12. Such a heat conduction portion 10 has minute void portions as gaps between the resin fibers 12 and the graphite (flake graphite) 11. By allowing a part of the constituent material of the joining portion 20 described in detail later to enter such a small space, the adhesion between the heat-conducting portion 10 and the joining portion 20 can be improved, and the durability of the heat-conducting sheet 100 can be improved. Further, the penetration of the constituent material of the joining portion 20 having a higher thermal conductivity than air by excluding the air in the minute space can contribute to further improvement of the thermal conductivity of the thermally conductive sheet 100.

(flake graphite)

The plurality of flaky graphite 11 included in each heat conduction portion 10 is oriented in a predetermined direction. That is, the flaky graphite 11 is oriented such that the thickness direction thereof is along the thickness direction of the layered heat conductive part 10 (particularly, the y-axis direction in the structure shown in fig. 3 and 4).

Accordingly, the thermally conductive sheet 100 has excellent thermal conductivity in the thickness direction (z-axis direction orthogonal to the y-axis) of the thermally conductive sheet 100.

In the present specification, the scale-like shape is defined as a shape in which the size of the main surface is sufficiently large with respect to the thickness, and may be, for example, a flat plate shape or a curved plate shape.

The arithmetic average value of the flatness (average flatness) of the flaky graphite 11 is preferably 2 or more, more preferably 3 or more and 100 or less, and further preferably 5 or more and 50 or less.

Note that the flatness of the flake graphite 11 means: the ratio (Ly/t) of the minor axis length Ly [ μm ] of the main surface of the flaky graphite 11 to the thickness t [ μm ] of the flaky graphite 11. As the average flatness of the flaky graphite 11, for example, an arithmetic average of flatness of 100 flaky graphite 11 randomly sampled by observation with a scanning electron microscope can be used. The arithmetic mean value (average minor axis length) of minor axis length Ly of the major surface of flake graphite 11 and the arithmetic mean value (average thickness) of thickness t of flake graphite 11, which will be described below, can be similarly determined.

The arithmetic average value (average short axis length) of the short axis lengths Ly of the main surfaces of the flaky graphite 11 is preferably 0.2 μm or more and 50 μm or less, more preferably 0.3 μm or more and 30 μm or less, and still more preferably 0.5 μm or more and 10 μm or less.

The flaky graphite 11 may be a flaky graphite, and expanded graphite is preferably used as the flaky graphite 11. This can further improve the strength, reliability, and thermal conductivity of the thermally conductive sheet 100.

Expanded graphite can be obtained by: for example, expanded graphite is obtained by using graphite having a layered crystal structure as a raw material, subjecting the raw material to an acid treatment with an oxidizing agent to form an interlayer compound, washing the interlayer compound, and subjecting the washed interlayer compound to a heat treatment at a high temperature to expand the interlayer compound.

The raw material of the expanded graphite is not particularly limited, and examples thereof include: graphite particles having a layered crystal structure such as natural graphite, kish graphite, and the like.

The oxidizing agent is not particularly limited, and examples thereof include: acids such as sulfuric acid, nitric acid, phosphoric acid, perchloric acid, and chromic acid, permanganic acid, periodic acid, hydrogen peroxide, and the like.

The temperature of the heat treatment is preferably 400 ℃ to 1000 ℃.

The content of the flake graphite 11 in the heat conductive portion 10 is not particularly limited, but is preferably 10 mass% or more and 90 mass% or less, more preferably 30 mass% or more and 85 mass% or less, and further preferably 50 mass% or more and 80 mass% or less.

This makes it possible to achieve both the thermal conductivity and flexibility of the thermal conductive portion 10 at a higher level.

(resin fiber)

Each heat conduction portion 10 includes resin fibers 12. Accordingly, the flake graphite 11 can be preferably held in the heat conduction portion 10. In addition, flexibility can be improved as compared with the case where a dense resin layer is provided. In addition, even when the thermally conductive sheet 100 is deformed, the whole thermally conductive sheet 100 can ensure a state in which the flaky graphite 11 are preferably in contact with each other.

Examples of the constituent material of the resin fiber 12 include: polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate, and polylactic acid; polyolefins such as polyethylene and polypropylene; polyamides such as aromatic polyamides (aromatic polyamide resins) such as polyparaphenylene terephthalamide, and aliphatic polyamides such as nylon 6 and nylon 6, 6; polyether ketones such as polyether ether ketone; thermoplastic resins such as acrylic resins, polyvinyl acetate, polyvinyl alcohol, polyphenylene sulfide, polyparaphenylene benzoxazole, polyimide, polycarbonate, polystyrene, acrylonitrile-butadiene-styrene resins (ABS resins), polyvinyl chloride resins, and epoxy resins; thermosetting resins such as epoxy resins, phenol resins, melamine resins, and unsaturated polyesters, copolymers of constituent monomers of these various resins (e.g., ethylene-vinyl alcohol copolymers), modified resins (e.g., maleic acid modified resins), polymer alloys, and the like, and 1 type selected from these resin fibers, or 2 or more types in combination can be used.

Among them, the resin fiber 12 is preferably made of an aromatic polyamide resin. This can further improve the strength of the heat-conducting portion 10 and the strength of the entire heat-conducting sheet 100. In addition, the heat-conductive sheet 100 can be made more excellent in heat resistance. In addition, unexpected melting, deformation, or the like of the resin fibers 12 at the time of molding or the like of the thermally conductive sheet 100 can be effectively prevented, and more precisely, flexibility of the thermally conductive sheet 100 can be made more excellent. As the resin fibers 12, a plurality of types of fibers having different compositions may be used.

The average length of the resin fibers 12 is not particularly limited, but is preferably 1.5mm or more and 20mm or less, more preferably 2.0mm or more and 18mm or less, and further preferably 3.0mm or more and 16mm or less. Accordingly, the heat conduction portion 10 can hold the flaky graphite 11 more favorably, and the flaky graphite 11 can be prevented from falling off more reliably. As a result, the thermally conductive sheet 100 can be made more excellent in durability and reliability. In addition, the heat conductive sheet 100 can be made more flexible.

In the thermally conductive sheet of the present embodiment, as the average length of the fibers, for example, an arithmetic average of the lengths of 100 fibers randomly selected by observation with a scanning electron microscope can be used.

The average width of the resin fibers 12 is preferably 1.0 μm or more and 50 μm or less, more preferably 2.0 μm or more and 40 μm or less, and still more preferably 3.0 μm or more and 30 μm or less. Accordingly, the heat conduction portion 10 can hold the flaky graphite 11 more favorably, and the flaky graphite 11 can be prevented from falling off more reliably. As a result, the thermally conductive sheet 100 can be made more excellent in durability and reliability. In addition, the heat conductive sheet 100 can be made more flexible.

In the thermally conductive sheet of the present embodiment, the average width of the fibers may be, for example, an arithmetic average of the widths of 100 fibers randomly selected by observation with a scanning electron microscope.

The content of the resin fibers 12 in the heat conductive portion 10 is not particularly limited, but is preferably 7 mass% or more and 90 mass% or less, more preferably 12 mass% or more and 70 mass% or less, and still more preferably 18 mass% or more and 50 mass% or less. This makes it possible to achieve both the thermal conductivity and flexibility of the thermal conductive portion 10 at a higher level.

(other Components)

The heat-conductive portion 10 may contain components other than the above components. Examples of such other components include: a binder, a coagulant, a plasticizer, a colorant, an antioxidant, an ultraviolet absorber, a light stabilizer, a softener, a modifier, an antirust agent, a filler, a surface lubricant, a preservative, a heat stabilizer, a lubricant, a primer, an antistatic agent, a polymerization inhibitor, a crosslinking agent, a catalyst, a leveling agent, a tackifier, a dispersant, an antiaging agent, a flame retardant, an anti-hydrolysis agent, a preservative, carbon fibers, carbon nanotubes, carbon nanofibers, cellulose nanofibers, fullerene, metal fibers, metal particles, and the like.

The thermal conductivity of the thermal conductive portion 10 at 20 ℃ in the thickness direction (z-axis direction) of the thermal conductive sheet 100 is preferably 10W/mK or more and 200W/mK or less, more preferably 15W/mK or more and 180W/mK or less, and still more preferably 20W/mK or more and 160W/mK or less. In the thermally conductive sheet of the present embodiment, the following values can be adopted as the thermal conductivity: heat was determined by a laser flash method in accordance with JIS (Japanese Industrial Standard) R1611Diffusion Rate (mm)²In/s), the product of thermal diffusivity and heat capacity (density x specific heat) was calculated.

The thickness of the heat-conducting portion 10 (the length of the heat-conducting portion 10 in the thickness direction, the length in the y-axis direction in the structure shown in fig. 3 and 4) is not particularly limited, but is preferably 50 μm or more and 300 μm or less, more preferably 55 μm or more and 270 μm or less, and still more preferably 60 μm or more and 250 μm or less. This makes it possible to achieve both the thermal conductivity and flexibility of the thermal conductive portion 10 at a higher level. In addition, the productivity of the thermally conductive sheet 100 can be further improved.

Note that, the plurality of heat conductive portions 10 included in the heat conductive sheet 100 may have the same thickness or different thicknesses, and in the case of having heat conductive portions 10 having different thicknesses, the ratio of the heat conductive portions whose thickness is included in the above range in the total number of the plurality of heat conductive portions 10 included in the heat conductive sheet 100 is preferably 50% or more, more preferably 70% or more, and further preferably 90% or more.

The volume ratio of the heat-conductive portion 10 in the entire heat-conductive sheet 100 is preferably 30 vol% or more and 90 vol% or less, more preferably 40 vol% or more and 85 vol% or less, and still more preferably 50 vol% or more and 82 vol% or less. This makes it possible to achieve both the thermal conductivity and flexibility of the thermal conductive portion 10 at a higher level.

(Joint part)

The heat conductive sheet 100 includes a plurality of joining portions 20, and the joining portions 20 join the heat conductive portions 10 so that the heat conductive portions 10 are in contact with the main surfaces of the heat conductive portions 10. In particular, in the present embodiment, the joint portion 20 extends in the x-axis direction.

The thermally conductive sheet 100 may include at least 1 joining portion 20, but in the illustrated configuration, a plurality of joining portions 20 are provided. More specifically, in the illustrated configuration, the thermally conductive sheet 100 includes: the plurality of joining portions 20 and the plurality of joining portions 20 are arranged such that the heat-conducting portions 10 and the joining portions 20 are alternately arranged in the y-axis direction and the heat-conducting portions 10 are arranged at both ends in the y-axis direction. In other words, when the number of the heat conductive portions 10 included in the heat conductive sheet 100 is n, the number of the joining portions 20 included in the heat conductive sheet 100 is (n-1).

The joint portion 20 is made of a flexible resin material. Further, the joint portion partially forms a void layer. Air or a gas generated when the resin material is cured is contained in the void layer. In addition, a part of the resin material penetrates into the void portion of the heat conduction portion. The ratio of the void layer in the joint portion is preferably 2 vol% or more and 30 vol% or less.

(resin Material)

The resin material (resin material having flexibility) constituting the joining portion 20 has a function of joining the adjacent heat conductive portions 10. The resin material constituting the joint portion 20 has flexibility. Therefore, the thermally conductive sheet 100 can preferably follow the surface shape of the heating element HG, for example. As a result, for example, heat conduction and heat dissipation can be performed preferably in accordance with the relationship with the above-described members. In addition, when the thermally conductive sheet 100 is deformed, the thermally conductive sheet 100 can be preferably prevented from being damaged or the like.

The resin material constituting the joint portion 20 is sufficiently dense, unlike the resin fibers 12 constituting the heat conductive portion 10. As described in detail below, such a joint 20 can be preferably formed using a resin material 20 'in a liquid state, or a resin material 20' in a sheet state (obtained by molding a composition in a liquid state into a sheet state).

The resin material constituting the joint portion 20 is not particularly limited, and a resin material other than a hard resin, for example, a flexible epoxy resin, a urethane resin, a rubber resin, a fluorine resin, a silicone resin, a thermoplastic elastomer, or the like can be preferably used.

As shown in fig. 5, the resin material constituting the joint portion 20 preferably includes: the polymer composition comprises a polyrotaxane 40 having a cyclic molecule 41, a first polymer 42 and a blocking group 43, and a second polymer 50, wherein the polyrotaxane 40 and the second polymer 50 are bonded via the cyclic molecule 41, the first polymer 42 has a linear molecular structure and includes the cyclic molecule 41 in a piercing manner, and the blocking group 43 is provided near both ends of the first polymer 42.

Accordingly, the bonding strength of the heat conductive portions 10 to each other via the bonding portions 20 and the durability of the heat conductive sheet 100 can be sufficiently improved, and the heat resistance (for example, the heat resistance that can withstand a use environment of 200 ℃. In addition, when the thermally conductive sheet 100 is manufactured, such a resin material is likely to penetrate into a minute void portion existing in the thermally conductive portion 10. Therefore, it is also advantageous to further improve the durability or thermal conductivity of the thermally conductive sheet 100.

In particular, in the case where the stress of deformation in the arrow direction is applied to the resin material (the joint portion 20) in the state shown in fig. 5A, the resin material can take the form shown in fig. 5B. That is, the cyclic molecule 41 can move along the first polymer 42 (in other words, the first polymer 42 can move within the cyclic molecule 41), and therefore the stress of deformation can be absorbed preferably within the resin material (in the joint 20). Therefore, even when a large deformation force (for example, an external force such as torsion) is applied, it is possible to effectively prevent damage to joint portion 20, separation of joint portion 20 from heat transfer portion 10, and the like.

Hereinafter, the resin material containing the polyrotaxane 40 and the second polymer 50 will be described in detail. The cyclic molecule 41 constituting the polyrotaxane 40 can move along the first polymer 42, but is preferably a cyclodextrin molecule which can be substituted, preferably selected from the group consisting of α -cyclodextrin, β -cyclodextrin, γ -cyclodextrin and derivatives thereof.

As described above, at least a portion of the cyclic molecules 41 in the polyrotaxane 40 are bonded to at least a portion of the second polymer 50.

Examples of the functional group of the cyclic molecule 41 (functional group to be bonded to the second polymer 50) include: -OH group, -NH₂A group, -COOH group, epoxy group, vinyl group, thiol group, photocrosslinking group, etc. Examples of the photocrosslinkable group include: cinnamic acid, coumarin, chalcone, anthracene, styrylpyridine, styrylpyridinium salt, styrylquinolinium salt, and the like.

When the amount of the cyclic molecules 41 that can be included to the maximum extent when the cyclic molecules 41 are included in a punctured state by the first polymer 42 is 1, the amount of the cyclic molecules 41 included in a punctured state by the first polymer 42 is preferably 0.001 or more and 0.6 or less, more preferably 0.01 or more and 0.5 or less, and still more preferably 0.05 or more and 0.4 or less. It should be noted that 2 or more different cyclic molecules 41 may be used.

Examples of the first polymer 42 constituting the polyrotaxane 40 include: polyvinyl alcohol, polyvinyl pyrrolidone, poly (meth) acrylic acid, cellulose-based resins (carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, etc.), polyacrylamide, polyethylene oxide, polyethylene glycol, polypropylene glycol, polyvinyl acetal-based resins, polyvinyl methyl ether, polyamine, polyethyleneimine, casein, gelatin, starch, etc., and/or copolymers thereof, polyolefin-based resins such as copolymer resins with polyethylene, polypropylene and other olefin-based monomers, polyester resins, polyvinyl chloride resins, polystyrene resins such as polystyrene or acrylonitrile-styrene copolymer resins, polymethyl methacrylate or (meth) acrylate copolymers, acrylic resins such as acrylonitrile-methyl acrylate copolymer resins, polycarbonate resins, polyurethane resins, vinyl chloride-vinyl acetate copolymer resins, acrylic resins such as acrylonitrile-methyl acrylate copolymer resins, polyvinyl chloride-vinyl acetate copolymer resins, polyvinyl alcohol-vinyl acetate copolymer resins, polyvinyl alcohol-based resins, polyvinyl alcohol-vinyl alcohol copolymer resins, polyvinyl alcohol-vinyl alcohol-co-copolymer resins, polyvinyl alcohol-co-copolymer, polyvinyl alcohol-based resins, polyvinyl alcohol-co-copolymer resins, and copolymer resins, Polyvinyl butyral resin and the like; and derivatives or modifications thereof, polyisobutylene, polytetrahydrofuran, polyaniline, acrylonitrile-butadiene-styrene copolymer (ABS resin), polyamides such as nylon, polydienes such as polyimide, polyisoprene, polybutadiene, polysiloxanes such as polydimethylsiloxane, polysulfones, polyamines, polyanhydrides, polyureas, polysulfides, polyphosphazenes, polyketones, polyphenylenes, polyhaloolefins, or derivatives thereof, with polyethylene glycol being particularly preferred.

The weight average molecular weight of the first polymer 42 is preferably 1 ten thousand or more, more preferably 2 ten thousand or more, and further preferably 3.5 ten thousand or more. Note that 2 or more different first polymers 42 may be used.

As the combination of the cyclic molecule 41 and the first polymer 42, preferably, the cyclic molecule 41 is α -cyclodextrin which may be substituted, and the first polymer 42 is polyethylene glycol.

The blocking group 43 constituting the polyrotaxane 40 is not particularly limited as long as it has a function of preventing the cyclic molecule 41 from being detached from the first polymer 42, and examples thereof include: dinitrobenzenes, cyclodextrins, adamantyls, trityls, luciferases, pyrenes, substituted benzenes (as the substituent, there may be 1 or more substituents, such as alkyl, alkoxy, hydroxyl, halogen, cyano, sulfonyl, carboxyl, amino, and phenyl), polynuclear aromatics which may be substituted, steroids, and the like. Examples of the substituent constituting the substituted benzene or substituted polynuclear aromatic compound include: alkyl, alkoxy, hydroxy, halo, cyano, sulfonyl, carboxy, amino, phenyl, and the like. The substituent may be present in 1 or more. It should be noted that more than 2 different capping groups 43 may also be used.

At least a part of the polyrotaxane 40 is bonded to the second polymer 50 through the cyclic molecule 41 in the resin material (the joint 20), but the resin material (the joint 20) may contain a polyrotaxane 40 which is not bonded to the second polymer 50, and the polyrotaxanes 40 may be bonded to each other.

The second polymer 50 is bonded to the polyrotaxane 40 via the cyclic molecule 41. Examples of the functional group to be bonded to the cyclic molecule 41, which the second polymer 50 has, include: -OH group, -NH₂A group, -COOH group, epoxy group, vinyl group, thiol group, photocrosslinking group, etc. Examples of the photocrosslinkable group include: cinnamic acid, coumarin, chalcone, anthracene, styrylpyridine, styrylpyridinium salt, styrylquinolinium salt, and the like.

Examples of the second polymer 50 include those having a skeleton of various resins such as: polyvinyl alcohol, polyvinyl pyrrolidone, poly (meth) acrylic acid, cellulose-based resins (carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, etc.), polyacrylamide, polyethylene oxide, polyethylene glycol, polypropylene glycol, polyvinyl acetal-based resins, polyvinyl methyl ether, polyamine, polyethyleneimine, casein, gelatin, starch, etc., and/or copolymers thereof, polyolefin-based resins such as copolymer resins with polyethylene, polypropylene and other olefin-based monomers, polyester resins, polyvinyl chloride resins, polystyrene resins such as polystyrene or acrylonitrile-styrene copolymer resins, polymethyl methacrylate or (meth) acrylate copolymers, acrylic resins such as acrylonitrile-methyl acrylate copolymer resins, polycarbonate resins, polyurethane resins, vinyl chloride-vinyl acetate copolymer resins, acrylic resins such as acrylonitrile-methyl acrylate copolymer resins, polyvinyl chloride-vinyl acetate copolymer resins, polyvinyl alcohol-vinyl acetate copolymer resins, polyvinyl alcohol-based resins, polyvinyl alcohol-vinyl alcohol copolymer resins, polyvinyl alcohol-vinyl alcohol-co-copolymer resins, polyvinyl alcohol-co-copolymer, polyvinyl alcohol-based resins, polyvinyl alcohol-co-copolymer resins, and copolymer resins, Polyvinyl butyral resin and the like; and derivatives or modifications thereof, polyisobutylene, polytetrahydrofuran, polyaniline, acrylonitrile-butadiene-styrene copolymer (ABS resin), polyamides such as nylon, polydienes such as polyimide, polyisoprene and polybutadiene, polysiloxanes such as polydimethylsiloxane, polysulfones, polyamines, polyacetic anhydrides, polyureas, polysulfides, polyphosphazenes, polyketones, polyphenylenes, and polyhaloolefins.

In addition, the second polymer 50 and the cyclic molecule 41 may also be chemically bonded by a crosslinking agent.

The molecular weight of the crosslinking agent is preferably less than 2000, more preferably less than 1000, still more preferably less than 600, and most preferably less than 400.

Examples of the crosslinking agent include: cyanuric chloride, trimesoyl chloride, terephthaloyl chloride, epichlorohydrin, dibromobenzene, glutaraldehyde, phenylene diisocyanate, toluene diisocyanate, divinylsulfone, 1' -carbonyldiimidazole, alkoxysilanes, and the like. It should be noted that 2 or more different crosslinking agents may be used.

The second polymer 50 may be a homopolymer or a copolymer. At least a part of the second polymer 50 is bonded to the polyrotaxane 40 via the cyclic molecule 41 in the resin material (the joint 20), but the resin material (the joint 20) may contain the second polymer 50 that is not bonded to the polyrotaxane 40, and the second polymers 50 may be bonded to each other. Note that 2 or more different second polymers 50 may be used.

The ratio of the content of the polyrotaxane 40 in the resin material (joint portion 20) to the content of the second polymer 50 is preferably 1/1000 or more in terms of a weight ratio.

(other Components)

The joint portion 20 may contain a component (other component) other than the above components. Examples of such components include: plasticizers, colorants, antioxidants, ultraviolet absorbers, light stabilizers, softeners, modifiers, rust inhibitors, fillers, surface lubricants, preservatives, heat stabilizers, lubricants, primers, antistatic agents, polymerization inhibitors, crosslinking agents, catalysts, leveling agents, tackifiers, dispersants, anti-aging agents, flame retardants, hydrolysis inhibitors, preservatives, and the like.

The thermally conductive sheet 100 of the present embodiment is in a layered form. The thickness T20 of the joint 20 (the length in the thickness direction of the joint 20 in a layer shape, the length in the y-axis direction in the structure shown in fig. 3 and 4) is not particularly limited, but is preferably 0.1 μm or more and 200 μm or less, more preferably 0.1 μm or more and 100 μm or less, and further preferably 0.1 μm or more and 50 μm or less. This makes it possible to achieve both the thermal conductivity and flexibility of the thermal conductive portion 10 at a higher level. In addition, the productivity of the thermally conductive sheet 100 can be made more excellent.

When the thermally conductive sheet 100 includes the plurality of joining portions 20, the plurality of joining portions 20 may have the same thickness or different thicknesses, and when the joining portions 20 have different thicknesses, the ratio of the thermally conductive portions included in the total number of the plurality of thermally conductive portions 10 included in the thermally conductive sheet 100 is preferably 50% or more, more preferably 70% or more, and still more preferably 90% or more.

In the illustrated configuration, the heat-conductive portion 10 and the joining portion 20 are flush with each other on both surfaces of the heat-conductive sheet 100, but the thickness T100 of the heat-conductive sheet 100 at the portion where the heat-conductive portion 10 is provided and the thickness T100 of the heat-conductive sheet 100 at the portion where the joining portion 20 is provided may be different. For example, in the illustrated configuration, each of the joint portions 20 is exposed on both main surfaces of the thermally conductive sheet 100, but at least 1 of the joint portions 20 may be exposed only on one surface of the thermally conductive sheet 100, or may not be exposed on any of the both main surfaces of the thermally conductive sheet 100.

The volume ratio of the joint portion 20 in the entire thermally conductive sheet 100 is preferably 10 vol% or more and 70 vol% or less, more preferably 15 vol% or more and 60 vol% or less, and still more preferably 18 vol% or more and 50 vol% or less. This makes it possible to achieve both the thermal conductivity and flexibility of the thermal conductive portion 10 at a higher level.

In the illustrated configuration, the boundary between the heat-conducting portion 10 and the joining portion 20 is clear, but the boundary between the heat-conducting portion 10 and the joining portion 20 may be unclear due to, for example, diffusion and compatibility of constituent materials of at least one of the heat-conducting portion 10 and the joining portion 20. In this case, the heat-conducting portion 10 may be a region in which the content of the flaky graphite 11 and the content of the resin fibers 12 are higher than the content of the flaky graphite and the resin fibers in the joining portion 20, and the joining portion 20 may be a region in which the content of the resin material is higher than the content of the resin material in the heat-conducting portion 10, and these regions may be distinguished from each other.

The use of the thermally conductive sheet 100 is not particularly limited, and the thermally conductive sheet can be used as various heat sinks, for example.

The thickness T100 (length in the z-axis direction) of the thermally conductive sheet 100 is preferably 0.2mm or more and 5mm or less, more preferably 0.3mm or more and 4mm or less, and further preferably 0.5mm or more and 3mm or less. Accordingly, the surface shape of the heating element HG can be better followed, and heat conduction and heat dissipation can be better performed. In addition, the flexibility and durability of the thermally conductive sheet 100 can be achieved at a higher level.

The surface roughness Ra of both main surfaces of the thermally conductive sheet 100 is preferably 0.1 μm or more and 100 μm or less, more preferably 0.2 μm or more and 80 μm or less, and further preferably 0.3 μm or more and 60 μm or less. This prevents the productivity of the heat conductive sheet 100 from being significantly reduced, and allows the heat conductive sheet to better follow the surface shape of the heating element HG, thereby allowing heat to be conducted and dissipated more efficiently.

The surface roughness Ra of the thermally conductive sheet 100 can be measured, for example, according to JIS B0601-. The surface roughness Ra of the thermally conductive sheet 100 can be adjusted by polishing or the like.

(Heat conductivity in thickness direction of the thermally conductive sheet 100)

0.2N/mm in the thickness direction of the thermally conductive sheet 100²When the thermally conductive sheet is pressed by the surface pressure of (2), the thermal conductivity in the thickness direction of the thermally conductive sheet 100 is defined as λ_0.2[W/m·K]At a thickness of 0.8N/m in the direction of the heat conductive sheet 100m²When the thermally conductive sheet is pressed by the surface pressure of (2), the thermal conductivity in the thickness direction of the thermally conductive sheet 100 is defined as λ_0.8[W/m·K]In this case, it is preferable that 1.5. ltoreq. lambda._0.8/λ_0.2A relationship of ≦ 3.5, more preferably satisfying 1.7 ≦ λ_0.8/λ_0.2A relationship of not more than 3.2, more preferably 1.9. ltoreq. lambda_0.8/λ_0.2A relation less than or equal to 3.0.

If λ_0.8/λ_0.2If the value of (b) is too small, the adhesion between the heat conductive sheet and the heating element HG or the heat radiating body may be insufficient depending on the conditions of the member in contact with the heat conductive sheet, and the heat conductivity may not be sufficiently exhibited. On the other hand, if λ_0.8/λ_0.2If the amount is too large, the stability of the shape may be lowered, and the durability of the thermally conductive sheet may be lowered, or the performance difference between the respective batches may be increased, and the stable performance may not be maintained. Thus, λ_0.8/λ_0.2Preferably, the content is within the above range.

The thermal conductivity of the thermally conductive sheet 100 in the thickness direction, measured on the main surface of the thermally conductive sheet 100 by the laser flash method, is preferably 10W/mK or more and 200W/mK or less, more preferably 15W/mK or more and 180W/mK or less, and still more preferably 20W/mK or more and 160W/mK or less.

Accordingly, the following effects are obtained: the high heat conductivity of the heat conducting sheet is ensured, and the heat conducting and radiating can be better realized.

0.2N/mm in the thickness direction of the thermally conductive sheet 100²The thickness of the thermally conductive sheet 100 is preferably 0.1mm or more and 5mm or less, more preferably 0.2mm or more and 4mm or less, and still more preferably 0.3mm or more and 3mm or less when the thermally conductive sheet is pressed by the surface pressure of (2).

Accordingly, the thickness of the heat conductive sheet having high followability absorbs the unevenness of the surface of the heating element HG and the heat radiating body, and the adhesion is sufficiently secured, whereby the interface thermal resistance is suppressed to be low, and the heat conduction and radiation effects can be further improved.

[ embodiment 2]

Next, a thermally conductive sheet according to embodiment 2 will be described with reference to fig. 6 to 7. In these drawings, fig. 6 is a schematic perspective view showing a thermally conductive sheet 200 according to embodiment 2, and fig. 7 is a schematic side view showing the thermally conductive sheet 200 according to embodiment 2. In the following description, differences from embodiment 1 will be mainly described, and descriptions of the same matters will be appropriately omitted.

In the above embodiment, the normal line N100 of the thermally conductive sheet 100 is orthogonal to the normal line N10 of the thermally conductive section 10 (the angle formed by these normal lines is 90 °), whereas in the thermally conductive sheet 200 of embodiment 2, the normal line N100 of the thermally conductive sheet 200 is not orthogonal to the normal line N10 of the thermally conductive section 10. As described above, in the thermally conductive sheet 200 of the present embodiment, the angle θ 1 formed by the normal N100 of the thermally conductive sheet 200 and the normal N10 of the thermally conductive portion 10 may be 25 ° or more and 90 ° or less, and the normal N100 of the thermally conductive sheet 200 and the normal N10 of the thermally conductive portion 10 may not be orthogonal to each other, as in the present embodiment. In such a case, the effects as described above are also obtained.

Further, the durability against the pressure in the thickness direction of the thermally conductive sheet 200 is improved by the fact that the normal N100 of the thermally conductive sheet 200 is not orthogonal to the normal N10 of the thermally conductive portion 10. The reason is considered to be that: in the case where the normal line N100 of the heat conductive sheet 200 is orthogonal to the normal line N10 of the heat conductive portion 10, when a pressure is applied in the thickness direction of the heat conductive sheet 200, the heat conductive portion 10 is bent due to difference in rigidity between the heat conductive portion 10 and the joint portion 20, and the heat conductive portion 10 and the joint portion 20 are easily peeled off, whereas when the normal line N100 of the heat conductive sheet 200 is not orthogonal to the normal line N10 of the heat conductive portion 10, when a pressure is applied in the thickness direction of the heat conductive sheet 200, the pressure contains a component of force in a direction of pressing the heat conductive portion 10 and the joint portion 20, and this component contributes to bringing the heat conductive portion 10 and the joint portion 20 into close contact.

As in the present embodiment, when the normal N100 of the thermally conductive sheet 200 is not orthogonal to the normal N10 of the thermally conductive portion 10, the angle θ 1 formed by the normal N100 of the thermally conductive sheet 200 and the normal N10 of the thermally conductive portion 10 is preferably 30 ° or more and 85 ° or less, more preferably 35 ° or more and 80 ° or less, and still more preferably 40 ° or more and 75 ° or less. Accordingly, the above effects are more remarkably exhibited.

[ embodiment 3]

Next, a thermally conductive sheet according to embodiment 3 will be described with reference to fig. 8. Fig. 8 is a schematic plan view showing a heat conductive sheet 300 according to embodiment 3. In the following description, differences from the above-described embodiment will be mainly described, and descriptions of the same matters will be appropriately omitted.

The thermally conductive sheet 300 of the present embodiment includes: a sheet main body 100' having the same configuration as the thermally conductive sheet 100 of the above embodiment; and a case 30 provided in contact with the outer periphery of the sheet main body. That is, the present embodiment has the same configuration as the above embodiment except for the case 30.

With such a configuration, even when the bonding strength between the heat-conducting portion 10 and the bonding portion 20 is relatively low, or when the strength of the heat-conducting portion 10 itself is low, or when the strength of the bonding portion 20 itself is low, or the like, it is possible to preferably prevent the heat-conducting sheet 300 from being damaged. In particular, even when the thermally conductive sheet 300 is deformed relatively largely when the thermally conductive sheet 300 is made to follow the surface of the heating body HG to which it is applied, it is possible to prevent the thermally conductive sheet 300 from being damaged. In addition, when the thermally conductive sheet 300 is manufactured, unexpected deformation can be effectively prevented, and the thermally conductive sheet 300 having a desired shape can be manufactured more preferably. In particular, the thermally conductive sheet 300 having a relatively small thickness (length in the z-axis direction) as described above can be manufactured more preferably.

Examples of the material constituting the case 30 include: polyolefins such as polyethylene, polypropylene, and polymethylpentene, various resin materials such as polyvinyl chloride, polyesters such as polyvinylidene chloride (PVDC) and polyethylene terephthalate, and copolymers thereof, various metal materials such as aluminum, copper, iron, and stainless steel, and the like, and 1 kind or a combination of 2 or more kinds thereof may be used, and polyvinylidene chloride is particularly preferable. Polyvinylidene chloride is excellent in adhesion to various resin materials and the like and also has self-adhesion, and therefore can be effectively prevented from accidentally falling off from the sheet main body 100', and the above-described effects can be more remarkably exhibited. Further, since polyvinylidene chloride also has a large tensile elastic modulus, handling ease in the production of the thermally conductive sheet 300 is particularly excellent.

The width W of the case 30 is preferably 3 μm or more and 2000 μm or less, more preferably 5 μm or more and 150 μm or less, and further preferably 30 μm or more and 1000 μm or less. Accordingly, the heat conductive sheet 100 is sufficiently excellent in flexibility, and the effect achieved by providing the case 30 is more remarkably exhibited. The width W of the case 30 may be constant or different for each portion.

The length of the housing 30 in the z-axis direction is not particularly limited, but is preferably 0.2mm or more and 5mm or less, more preferably 0.3mm or more and 4mm or less, and further preferably 0.5mm or more and 3mm or less.

In the configuration of fig. 14C described below, the case 30 is provided on the entire outer periphery of the sheet main body 100', but may be provided only on a part of the outer periphery of the sheet main body 100'. For example, the case 30 may be provided only on the side parallel to the y-axis of the sheet main body 100' and a part of the side parallel to the x-axis connected to these sides. In such a case, the above-described effects are also sufficiently exhibited. In addition, the amount of material used for the housing 30 can be reduced, which is advantageous in terms of resource saving, cost reduction, and the like.

(use form of Heat-conductive sheet)

Next, a use mode of the heat conductive sheet of the present embodiment will be explained. The thermally conductive sheet of the present embodiment is excellent in thermal conductivity, particularly thermal conductivity in the thickness direction, and also excellent in flexibility. Therefore, it can be preferably used for cooling the high-temperature member as the heat generating body HG. The thermally conductive sheet of the present embodiment is generally used so as to be in contact with at least a part of the surface of the high-temperature member. The heat conductive sheet of the present embodiment may be cut and used as needed depending on the size, shape, and the like of the high-temperature member to be used. Further, a plurality of heat conductive sheets may be applied to a single high temperature member.

The high-temperature member is not particularly limited as long as it is a member having a temperature higher than the environment in which the high-temperature member is placed. For example, there may be mentioned: a Central Processing Unit (CPU) of a computer, a Graphic Processing Unit (GPU), an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), and other electronic components, such as a Light Emitting Diode (LED), a liquid crystal, and an Electroluminescence (EL).

The maximum temperature of the surface of the high-temperature member to which the thermally conductive sheet is applied (the maximum temperature reached without the thermally conductive sheet applied) is preferably 40 ℃ or higher and 250 ℃ or lower, more preferably 50 ℃ or higher and 200 ℃ or lower, and still more preferably 60 ℃ or higher and 180 ℃ or lower. Examples of such high-temperature components include: electronic components such as a Central Processing Unit (CPU) of a computer and a Graphic Processing Unit (GPU), electronic components such as a Light Emitting Diode (LED), a liquid crystal, Electroluminescence (EL), and various batteries such as a lithium ion battery.

[ method for producing thermally conductive sheet of embodiment 1]

Next, a method for manufacturing the thermally conductive sheet of the embodiment will be described. First, a method for producing the thermally conductive sheet 100 of embodiment 1 will be described with reference to fig. 9A to 11. In these drawings, fig. 9A to 9C are schematic cross-sectional views showing a method for producing a thermally conductive sheet according to embodiment 1, and fig. 10 and 11 are schematic cross-sectional views showing another example of a lamination step.

The method for producing a thermally conductive sheet according to embodiment 1 includes:

a heat-conductive-portion-forming sheet preparation step of preparing a heat-conductive-portion-forming sheet 10' for forming the heat conductive portion 10, as shown in fig. 9A;

a lamination step of laminating the heat-conduction-portion-forming sheets 10 'with the resin material 20' interposed therebetween to obtain a laminate 60, as shown in fig. 9B;

a cutting step of cutting the stacked body 60 in the stacking direction of the heat-conducting-portion-forming sheets 10', as shown in fig. 9C.

Accordingly, it is possible to provide a method for manufacturing a thermally conductive sheet, which can preferably manufacture a thermally conductive sheet having excellent thermal conductivity in the thickness direction and also excellent flexibility. Hereinafter, each step will be described in detail.

(preparation of sheet for Forming Heat-conductive portion)

In the heat-conductive-portion-forming sheet preparation step, as shown in fig. 9A, a heat-conductive-portion-forming sheet 10' for forming the heat conductive portion 10 is prepared. As the heat-conducting portion-forming sheet 10', for example, a sheet obtained by mixing flake-like graphite (flake-like graphite) 11 with resin fibers 12 can be used. The thermally conductive portion-forming sheet 10 'obtained by the mixed crystal is preferably oriented such that the thickness direction of the flaky graphite 11 is along the thickness direction of the thermally conductive portion-forming sheet 10'.

It is preferable to form the sheet by mixing and then to perform a drying treatment. This makes it possible to remove water used in the mixed sheet and to facilitate the handling. Further, the shape stability and strength of the heat-conducting portion-forming sheet 10' are improved.

After the sheet is formed into a sheet by mixing, the sheet is preferably subjected to heat and pressure treatment in the thickness direction of the sheet. This enables the flaky graphite 11 to be more favorably oriented. Further, the shape stability and strength of the heat-conducting portion-forming sheet 10' are improved. In addition, the water used in the mixed paper making can be removed, and the processing becomes easy.

In particular, the heat-conducting portion-forming sheet 10' is preferably produced by a method having the following steps. That is, the heat-conducting portion-forming sheet 10' is preferably produced by a method having: a mixing step of mixing and kneading scaly graphite (scaly graphite) 11 and resin fibers 12; a first pressing step (first pressing step) of pressing the mixed sheet in the thickness direction thereof; a drying step; and a second pressing step (second pressing step) of heating the kneaded material while pressing the same in the thickness direction.

The first pressing step may preferably be performed at room temperature (e.g., 10 ℃ or higher and 35 ℃ or lower). The pressing pressure in the first pressing step may be, for example, 1MPa to 30 MPa.

The drying step may be performed by pressure reduction, heating, or natural drying, and in the case of performing by heating, the heating temperature may be set to 40 ℃ or higher and 100 ℃ or lower.

The heating temperature (hot stamping surface temperature) in the second pressing step may be set to, for example, 100 ℃ to 400 ℃. The pressing pressure in the second pressing step may be, for example, 10MPa to 40 MPa.

The constituent materials (the flake graphite 11, the resin fibers 12, and the like) of the heat-conducting-portion-forming sheet 10' may be the same as those of the case 30, and preferably satisfy the same conditions as those of the constituent materials described for the heat-conducting portion 10. Accordingly, the same effects as those described above are obtained.

The thickness of the heat-conducting portion-forming sheet 10' is generally the same as the thickness of the heat-conducting portion 10. In this step, a plurality of the heat-conducting-portion-forming sheets 10 'are usually prepared, and for example, only 1 strip-shaped (cloth-like) heat-conducting-portion-forming sheet 10' may be prepared. In such a case, a laminate can be preferably obtained in the subsequent lamination step.

(laminating step)

In the lamination step, as shown in fig. 9B, the heat-conductive-portion-forming sheets 10 'are laminated via the resin material 20' to obtain a laminated body 60. The resin material 20' should be a joint portion 20 in the thermally conductive sheet 100. The resin material 20' used in this step may be in a liquid state or a sheet state (for example, a prepreg or the like).

The resin material 20' corresponds to the resin material constituting the joint portion 20. More specifically, the resin material 20' may be a material that satisfies the same conditions as those of the resin material constituting the joint 20, or may be a precursor thereof. Examples of the precursor include monomers, dimers, oligomers, and prepolymers having a lower degree of polymerization, and resin materials having a lower degree of crosslinking.

The resin material (resin material composition) 20' may contain components other than the above components. Examples of such components include: polymerization initiators, crosslinking agents, solvents, and the like. When the resin material 20' used in this step is in a liquid state, the resin material 20' is usually applied to the surface of the heat-conducting portion-forming sheet 10' in this step. The amount of resin material 20 'applied may be the same or different for each portion of the heat-conducting portion-forming sheet 10'. The resin material 20' may be applied to the entire surface of the heat-conductive-portion-forming sheet 10', or may be applied only to a part of the surface of the heat-conductive-portion-forming sheet 10 '.

In the configuration shown in fig. 9A to 9B, a plurality of prepared single heat-conducting-part-forming sheets 10' are laminated with the resin material 20' interposed therebetween, and the heat-conducting-part-forming sheet 10' (particularly, a strip-shaped heat-conducting-part-forming sheet 10') to which the resin material 20' is applied may be wound, for example, as in a laminated body 60B shown in fig. 10. In addition, the laminate 60C can also be obtained by: as in the laminate 60C shown in fig. 11, the heat-conductive-portion-forming sheet 10' (particularly, the strip-shaped heat-conductive-portion-forming sheet 10') provided with the resin material 20' is folded in a bellows shape, thereby obtaining the laminate 60C.

In this step, at least the heat-conducting portion-forming sheet 10 'may be laminated via the resin material 20', but other processes may be performed as necessary. For example, a heating process for softening or melting the resin material 20' may be performed, and when the resin material 20' contains a solvent, a drying process by, for example, reducing pressure, heating, or air-drying may be performed, a polymerization process or a crosslinking process for increasing the degree of polymerization or crosslinking of the resin material 20' may be performed, or a pressing process (pressure bonding process) for improving the adhesion between the heat-conductive-part-forming sheet 10' and the resin material 20' (the adhesion between the heat conductive part 10 and the joining part 20) may be performed.

In addition, in this step, the target laminated body 60 can also be obtained as follows: a unit in which a plurality of heat-conducting-portion-forming sheets 10 'are joined by a resin material 20' is prepared in advance, and the unit is laminated and joined.

(cutting step)

In the cutting step, as shown in fig. 9C, the stacked body 60 is cut in the stacking direction of the heat-conducting-portion-forming sheets 10' (the thickness direction of the stacked body 60). Accordingly, the above-described thermally conductive sheet 100 is obtained. In particular, the plurality of heat conductive sheets 100 are obtained by cutting the sheet a plurality of times. In this case, by adjusting the thickness at the time of cutting, the thermally conductive sheet 100 having a desired thickness can be obtained. In the case where a plurality of the thermally conductive sheets 100 are obtained, the respective thermally conductive sheets 100 may have the same thickness or may have different thicknesses from each other. The stacked body 60 may be cut so that the thicknesses of the respective portions of 1 thermally conductive sheet 100 are different from each other.

In addition, this step may be performed in a state where the laminate 60 is cooled. Accordingly, for example, the elastic deformation of the resin material 20' in the present step can be more effectively suppressed, and the present step can be performed more efficiently. In addition, even when the cutting thickness (the thickness T100 of the thermally conductive sheet 100) is relatively thin, this step can be preferably performed, and a decrease in yield can be efficiently prevented. When the present step is performed in a state where the laminate 60 is cooled, the temperature of the laminate 60 in the present step is preferably 10 ℃ or lower, more preferably 0 ℃ or lower, and still more preferably-10 ℃ or lower. Accordingly, the above-described effects are more remarkably exhibited.

[ method for producing thermally conductive sheet of embodiment 2]

Next, a method for producing a thermally conductive sheet according to embodiment 2 will be described with reference to fig. 12A to 13B. Fig. 12A to 12D are schematic cross-sectional views showing a method for producing a thermally conductive sheet according to embodiment 2. Fig. 13A to 13B are vertical sectional views schematically showing changes in the thickness of the thermally conductive sheet and changes in the inclination of the thermally conductive portion before and after the pressing step, fig. 13A is a view showing a state before the pressing step, and fig. 13B is a view showing a state after the pressing step. In the following description, differences from the above-described embodiment will be mainly described, and descriptions of the same matters will be appropriately omitted.

The method for producing a thermally conductive sheet according to embodiment 2 includes:

a heat-conductive-portion-forming sheet preparation step of preparing a heat-conductive-portion-forming sheet 10' for forming the heat conductive portion 10, as shown in fig. 12A;

a lamination step of laminating the heat-conduction-portion-forming sheets 10 'with the resin material 20' interposed therebetween to obtain a laminate 60, as shown in fig. 12B;

a cutting step of cutting the stacked body 60 in a direction inclined at a predetermined angle with respect to the stacking direction of the heat-conducting-portion-forming sheets 10', as shown in fig. 12B; and

a pressing step of pressing the sheet member 200 obtained by cutting in the thickness direction thereof as shown in fig. 12C.

In the cutting step shown in fig. 12C, the stacked body 60 is cut in a direction inclined by a predetermined angle θ 2 with respect to the stacking direction of the heat-conducting-portion-forming sheets 10' (the thickness direction of the stacked body 60). In other words, the manufacturing method is the same as that of embodiment 1, except that the laminate 60 has a different cutting direction and a pressing step. With such a configuration, as shown in fig. 6, it is possible to preferably manufacture the heat conductive sheet 100 in which the normal N100 of the heat conductive sheet 200 is not orthogonal to the normal N10 of the heat conductive portion 10.

Further, by providing the pressing step shown in fig. 12C after the cutting step as described above, the adhesion between the heat-conductive portion 10 and the joining portion 20 is further improved than before the pressing step, and the heat-conductive sheet can be made more excellent in durability. Further, the heat conductive sheet 200 can be preferably made thinner, and the angle formed by the normal N100 of the heat conductive sheet 200 and the normal N10 of the heat conductive portion 10 in the heat conductive sheet 200 can be further preferably adjusted (see fig. 13A and 13B).

The cutting direction of the laminate 60 in the cutting step preferably satisfies the following conditions. That is, the angle θ 2 between the cutting direction and the stacking direction of the heat-conducting-portion-forming sheets 10 '(the normal direction of the heat-conducting-portion-forming sheets 10', the thickness direction of the stacked body 60) is preferably 5 ° or more and 85 ° or less, more preferably 7 ° or more and 60 ° or less, further preferably more than 10 ° and 50 ° or less, and most preferably more than 15 ° and 40 ° or less. Accordingly, the above effects are more remarkably exhibited.

The pressure in the pressing step is not particularly limited, but is preferably 0.01MPa to 1MPa, more preferably 0.03MPa to 0.7MPa, and still more preferably 0.05MPa to 0.5 MPa. Accordingly, the above effects are more remarkably exhibited.

[ method for producing thermally conductive sheet according to embodiment 3]

Next, a method for producing a thermally conductive sheet according to embodiment 3 will be described with reference to fig. 14A to 14D. Fig. 14A to 14D are schematic cross-sectional views showing a method for producing a thermally conductive sheet 300 according to embodiment 3. In the following description, differences from the above-described embodiment will be mainly described, and descriptions of the same matters will be appropriately omitted.

The method for manufacturing the thermally conductive sheet 300 according to embodiment 3 includes:

a heat-conductive-portion-forming sheet preparation step of preparing a heat-conductive-portion-forming sheet 10' for forming the heat conductive portion 10, as shown in fig. 14A;

a lamination step of laminating the heat-conduction-portion-forming sheets 10 'with the resin material 20' interposed therebetween to obtain a laminate 60, as shown in fig. 14B;

a case-forming film disposing step of disposing a case-forming film 30' on the laminate 60 as shown in fig. 14C; and

a cutting step of cutting the laminated body 60 provided with the case forming film 30 'in the laminating direction of the heat-conducting portion forming sheet 10', as shown in fig. 14D.

In other words, the manufacturing method is the same as the manufacturing method of embodiment 1 except that a case forming film providing step is further included between the laminating step and the cutting step.

With such a configuration, the heat conductive sheet 300 can function as the housing 30 as described above. In addition, for example, the stacked body 60 can be suppressed from being deformed unexpectedly in the subsequent cutting step, and the occurrence of an unexpected thickness difference in the thermally conductive sheet 300 can be more effectively prevented.

Note that, although fig. 14D shows a case where the stacked body 60 is cut in the stacking direction of the heat-conducting-portion-forming sheets 10 '(the thickness direction of the stacked body 60) in the cutting step, the stacked body 60 may be cut in a direction inclined at a predetermined angle with respect to the stacking direction of the heat-conducting-portion-forming sheets 10' (the thickness direction of the stacked body 60) as in embodiment 2 described above. In the method for manufacturing the thermally conductive sheet 300 according to embodiment 3, the pressing step described in embodiment 2 may be further provided after the cutting step.

(case forming film setting step)

In the case forming film disposing step shown in fig. 14C, the case forming film 30' is disposed on the laminate 60. The case forming film 30' may be provided in any form, and is preferably provided on at least a part of two side surfaces (surfaces in the thickness direction) of the laminate 60 facing each other and an upper surface and a lower surface (an upper surface and a lower surface in the lamination direction of the laminate 60) connected to the side surfaces. With such a configuration, the heat conductive sheet 300 can more effectively function as the case 30 as described above. In addition, for example, the laminate 60 can be more effectively suppressed from being accidentally deformed in the subsequent cutting step, and the occurrence of an accidental thickness difference in the thermally conductive sheet 300 can be more effectively prevented.

In particular, in the illustrated configuration, the case forming film 30' is continuously provided on the entire upper and lower surfaces, except for the two opposing side surfaces of the laminate 60. Accordingly, the above-described effects are more remarkably exhibited.

In the thermally conductive sheet 300 of embodiment 3, the case setting step is performed by winding the case forming film 30' around the laminated body 60. Accordingly, in this step, the film 30' for forming the case can be more effectively prevented from being unintentionally peeled off or falling off, and the above-described effects can be more reliably exhibited. In addition, the shape stability of the laminate 60 in the cutting step becomes particularly excellent.

When the case forming film 30 'is wound around the laminate 60, the thickness of the case forming film 30' is preferably 3 μm or more and 100 μm or less, more preferably 5 μm or more and 80 μm or less, and still more preferably 7 μm or more and 50 μm or less. Accordingly, the heat conductive sheet 300 is sufficiently excellent in flexibility, and the above-described effects are more remarkably exhibited.

The constituent material of the case forming film 30' may be the same as the constituent material of the case 30, and preferably satisfies the same conditions as those of the case 30. Accordingly, the effects as described above are obtained.

[ method for producing thermally conductive sheet according to embodiment 4]

In the above example, the method of laminating the heat-conducting portion-forming sheets 10 'with the resin material 20' interposed therebetween was described, but the present invention is not limited to the method of obtaining the laminated structure of the heat-conducting portion and the joining portion. For example, the laminated structure of the heat conduction portion and the joint portion may also be obtained by: the resin material 20' is laminated in a state where the heat-conducting portion-forming sheet 10' is impregnated with the resin material 20', and the resin material 20' is cured with respect to the laminated heat-conducting portion-forming sheet 10 '. In addition, the laminating method may be a method of laminating a plurality of heat-conducting-portion-forming sheets 10 'cut into a sheet shape, or a method of winding or bending a single heat-conducting-portion-forming sheet 10' formed in advance to form a laminated state.

For example, as shown in fig. 15, a wound body RL1 obtained by winding the produced heat-conductive-portion-forming sheet 10' in a roll shape is prepared in advance. Next, one end of the heat-conducting-portion-forming sheet 10 'is pulled out from the roll RL1 and impregnated with the liquid resin material 20'. For example, the heat-conducting-portion-forming sheet 10 'pulled out from the roll is immersed in the resin tank BT in which the liquid resin material 20' is accumulated. Alternatively, coating may be performed by using a contact coating machine, a die coating machine, or the like, or by spraying.

The thermally conductive portion-forming sheet 10 'impregnated or coated with the resin material 20' in this manner is wound again around another roll RO 2. In this state, the resin material 20' is cured, whereby a laminate 60D can be obtained. For example, by using a thermoplastic resin or an ultraviolet-curable resin, a laminate 60D obtained by curing the resin material 20' by heating or irradiating with ultraviolet rays or the like the laminated heat-conductive-portion-forming sheet 10' impregnated with the uncured resin material 20' can be obtained as a wound body RL 2. When curing the resin material 20', for example, the roll RL2 placed in the closed space CS is heated by the heater HT or irradiated with ultraviolet rays while being rotated as shown in fig. 16.

In addition, according to this method, the resin content can be adjusted in an uncured state of the resin material 20'. By measuring the weight of the roll RL1 in advance, the amount of resin material 20 'impregnated can be calculated from the difference between the measured weight of the roll RL2 containing the resin material 20'. If the amount of impregnation of the resin material 20' is too large relative to the heat conductor forming sheet 10', the wound body RL2 may be rotated to throw off the resin material 20' by centrifugal separation, thereby adjusting the resin material to a desired impregnation amount. In addition, when the amount of impregnation of the resin material 20' is too small, the process may be returned to the impregnation step to impregnate the heat-conductive-part-forming sheet 10' with the resin material 20' again. In addition, the impregnation amount can also be adjusted as follows: the roll RL2 is placed in an uncured state of the liquid resin material 20', and a part of the resin material 20' is allowed to naturally drip. However, in this case as well, it is preferable to rotate the wound body RL2 at a constant speed so that the resin material 20' is uniformly distributed on the wound body RL 2.

The resin material 20 'can be cured with respect to the roll RL2 containing the resin material 20' impregnated in a desired amount in this manner, obtaining a laminated body 60D. Then, the laminate 60D is subjected to a cutting step. As shown in the cross-sectional view of fig. 17, the cutting is performed as follows: the cut surfaces are parallel to each other with a plane perpendicular to the winding axis direction of the wound body RL2 as a cut surface, and the interval between the cut surfaces is cut in accordance with the thickness of the heat conductive sheet 100. Thus, a base paper of the cut heat conductive sheet was obtained. Further, the base paper of the obtained thermally conductive sheet is cut into a desired size (for example, a rectangle shown by a broken line in fig. 17) as necessary to obtain the thermally conductive sheet 100. In the obtained thermally conductive sheet 100, the interface between the thermally conductive portion 10 and the joining portion 20 is not linear as shown in fig. 3, but is curved in an arc shape. In addition, the pattern of the heat conductive sheet base paper is slightly different depending on the cutting position of the heat conductive sheet base paper.

The cutting position of the stacked body 60D is not limited to the plane orthogonal to the roller RO2 shown in fig. 17, and for example, as shown in the side view of fig. 18, the stacked body may be cut on a plane inclined with respect to the roller RO 2. In this cutting method, the interface between the heat-conductive portion 10 and the joint portion 20 of the cut heat-conductive sheet base paper can be inclined as shown in the cross-sectional view of fig. 7.

Alternatively, as shown in the sectional views of fig. 19A to 19C, a plane parallel to the roller RO2 of the roll RL2 may be a cut surface. In this case, the cut surfaces are also parallel to each other, and the interval between the cut surfaces is cut in accordance with the thickness of the heat conductive sheet 100. Thus, a base paper of the cut heat conductive sheet was obtained. Further, the base paper of the obtained thermally conductive sheet is cut into a desired size as needed to obtain the thermally conductive sheet 100. In the obtained thermally conductive sheet 100, the patterns of the thermally conductive portion 10 and the joining portion 20 are not equal in width or angle at each position as shown in fig. 3, but are slightly inclined. Further, the width and angle of the heat conductive sheet base paper are slightly different depending on the cutting position of the heat conductive sheet base paper. In the example of fig. 19A, the cutting position is set to a position not passing through the roller RO2, but the cutting position is not limited to this example, and for example, as shown in the cross-sectional view of fig. 19A, a cross-section along a radius passing through the roller RO2 may be set. With this cutting method, the patterns of the heat-conductive portion 10 and the joint portion 20 of the cut heat-conductive sheet base paper can be made substantially constant regardless of the cutting position, and a homogeneous heat-conductive sheet 100 can be obtained from one laminated body 60D. Alternatively, as shown in the sectional view of fig. 19C, the cutting may be performed in a fixed region centered on the roller RO2 with the cut surfaces parallel to each other, and the remaining region may be set in a direction perpendicular to the cut surfaces. In this method, the cutting surface may not be inclined as in the cross-sectional view of fig. 19B, but only two directions, i.e., the vertical direction and the horizontal direction, may be set in fig. 19C, so that there is an advantage that the cutting can be easily performed.

In the above configuration of winding the heat-conducting-portion-forming sheet 10', the configuration is not necessarily limited to the configuration of winding the sheet into a perfect circle in section as shown in fig. 15, and the sheet may be formed into an elliptical shape, a track shape, or the like. In the above example, the configuration in which the core is wound by using the roll RO2 is shown, but a coreless wound body without a core may be used.

Further, in the above example, the heat conductive sheet 100 is described as an example of being rectangular in plan view, but it is needless to say that the shape of the heat conductive sheet 100 may be appropriately set according to the shape of the heating element HG or the heat sink.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, the method for producing the thermally conductive sheet may include other steps (pretreatment step, intermediate treatment step, post-treatment step, and the like) in addition to the above steps. For example, as the post-treatment of the cutting step, a step of polishing the surface of the sheet may be provided. Accordingly, the heat conduction portion can be exposed to the outside more favorably, and the surface roughness Ra can be adjusted more favorably. In the method for producing a thermally conductive sheet according to embodiment 2, the pressing step may be omitted.

The thermally conductive sheet of the present invention is not limited to the thermally conductive sheet produced by the above-described method, and may be produced by any method. The heat conductive sheet of the present invention may have a structure other than the heat conductive portion, the joining portion, and the case.

The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited thereto. In particular, the treatment under temperature conditions, not shown, and the measurement were carried out at 20 ℃.

(1) Production of thermally conductive sheet

The thermally conductive sheets of the examples and comparative examples were produced in the following manner.

(example 1)

(production of sheet for Forming Heat-conductive portion)

First, an aromatic polyamide resin as a resin fiber and expanded graphite as flake graphite were mixed and kneaded (mixing and kneading step), then, a pressing treatment was performed at 20 ℃ under a pressing pressure of 1MPa (first pressing step), further, a drying treatment was performed at 140 ℃, then, a pressing treatment was performed at 5MPa under a pressing pressure of 2 minutes under 180 ℃ (second pressing step), and further, the sheet was cut into a square of 150mm × 150mm, thereby obtaining a plurality of sheets for forming a heat conductive portion. In the obtained heat-conducting portion-forming sheet, the flaky graphite is oriented so that the thickness direction thereof is along the thickness direction of the heat-conducting portion-forming sheet. The thickness of the obtained sheet for forming a heat conductive portion was 65 μm.

(production of laminate)

Next, 1 of the heat-conductive-portion-forming sheets was placed on a glass plate, and 3g of a solvent-free one-liquid type of a SeRM Elastomer (manufactured by Advanced Soft Materials co., ltd.) made of an Elastomer was applied as a resin material to the entire one main surface (upper surface) of the heat-conductive-portion-forming sheet. The SeRM Elastomer comprises: a polyrotaxane which has a cyclic molecule, a first polymer having a linear molecular structure and including the cyclic molecule in a piercing manner, and blocking groups provided near both ends of the first polymer; and a second polymer molecule, the polyrotaxane and the second polymer being bonded via a cyclic molecule, and the SeRM Elastomer satisfying the above preferable conditions.

Next, the thermally conductive section-forming sheet to which the resin material is applied is placed on the thermally conductive section-forming sheet to which the resin material is applied. By repeating the coating of the top-most sheet for forming a heat conductive portion with a SeRM Elastomer (manufactured by Advanced Soft Materials co., ltd.) and the placing of the sheet for forming a heat conductive portion without a resin material thereon, a laminate having 25 sheets for forming a heat conductive portion and 25 resin material layers was obtained.

Next, the laminate was sandwiched by 2 glass plates, and the layers were pressure bonded using a jig. In this state, the resin material, SeRM Elastomer, was cured by heating at 150 ℃ for 3 hours.

(production of thermally conductive sheet)

Next, the laminate obtained in this manner (laminate in a state in which the SeRM Elastomer as the resin material is cured) is cut in the thickness direction thereof (cutting step), and the surface is polished with paper or a polishing tool (polishing step), thereby obtaining the thermally conductive sheet shown in fig. 2 to 4.

The thermally conductive sheet obtained in this manner includes a plurality of thermally conductive portions in a layered form and a joining portion joining the respective thermally conductive portions, and is a sheet as a whole. The heat-conducting portion is made of a material including graphite in a flake form and resin fibers, and is provided from one main surface to the other main surface of the heat-conducting sheet, the joining portion is made of a flexible resin material, the graphite is oriented so that the thickness direction thereof is along the thickness direction of the layered heat-conducting portion, and an angle formed between a normal line of the heat-conducting sheet and a normal line of the heat-conducting portion is 90 °.

In other words, the thermally conductive sheet obtained in the present embodiment is constituted by: when axes intersecting each other in the plane direction of the thermally conductive sheet are set as x-axis and y-axis and an axis intersecting the x-axis and y-axis is set as z-axis, the thermally conductive sheet has a thermal conductivity higher in the z-axis direction than in the y-axis direction, and is provided with a plurality of thermally conductive portions extending in the x-axis direction and a joining portion 20 made of a resin material and joining the respective thermally conductive portions in the y-axis direction, the thermally conductive portions being made of a material containing graphite and resin fibers, the graphite being in a flake shape and having an orientation such that the thickness direction of the flake is in the y-axis direction.

The thickness of the thermally conductive sheet obtained in this way was 0.3 mm. The surface roughness Ra of both surfaces of the heat conductive sheet was 50 μm. In the thermally conductive sheet, the thickness of the thermally conductive portion formed of the thermally conductive portion-forming sheet was 65 μm, and the thickness of the bonding portion 20 formed of a cured product of the SeRM Elastomer as a resin material was 100 μm. The content of the resin fibers in the heat conductive portion was 25 mass%, and the content of the flaky graphite was 75 mass%.

(examples 2 to 5)

A thermally conductive sheet was produced in the same manner as in example 1, except that conditions of the resin fibers and the flake graphite for producing the thermally conductive portion-forming sheet were changed, and the type of the resin material for forming the joining portion, the coating conditions, and the lamination conditions of the thermally conductive portion-forming sheet and the resin material were adjusted to have the configurations shown in table 1.

(example 6)

A thermally conductive sheet was produced in the same manner as in example 1 above, except that the cutting step was performed such that the angle formed between the stacking direction of the thermally conductive portion-forming sheets (the normal direction of the thermally conductive portion-forming sheets) and the cutting direction was 19 °, and a pressing step for pressing the sheet member obtained in the cutting step in the thickness direction was provided between the cutting step and the polishing step (see fig. 2, 6, and 7). The pressure in the pressing step was set to 0.2 MPa.

(examples 7 to 10)

A thermally conductive sheet was produced in the same manner as in example 6, except that conditions of the resin fibers and the flake graphite for producing the thermally conductive portion-forming sheet were changed, and an angle formed by the laminating direction of the thermally conductive portion-forming sheets (the normal direction of the thermally conductive portion-forming sheets) and the cutting direction in the cutting step was adjusted, while the type of the resin material for forming the joint portion, the coating condition, the laminating condition of the thermally conductive portion-forming sheets and the resin material, and the angle formed by the laminating direction of the thermally conductive portion-forming sheets (the normal direction of the thermally conductive portion-forming sheets) and the cutting direction were adjusted.

(example 11)

First, a laminate including 25 sheets of the sheet for forming a heat conduction portion and 25 resin material layers (a laminate in which the SeRM Elastomer as the resin material is cured) was obtained in the same manner as in example 1.

Next, the entire of the two opposing side surfaces, upper surface and lower surface of the laminate were wound with a 11 μm polyvinylidene chloride film, and a case-forming film having an average width of 100 μm was provided.

Thereafter, the laminate obtained in this manner in the state where the case forming film is provided is cut in the thickness direction thereof (cutting step), and the surface is polished with paper or a polishing tool (polishing step), thereby obtaining a thermally conductive sheet including a sheet main body including a thermally conductive portion and a joining portion, and a case provided so as to be in contact with the outer periphery of the sheet main body (see fig. 8).

(examples 12 to 15)

A thermally conductive sheet was produced in the same manner as in example 6, except that conditions of the resin fibers and the flake graphite for producing the thermally conductive portion-forming sheet were changed, and conditions of application of the resin material for forming the joining portion, conditions of lamination of the thermally conductive portion-forming sheet and the resin material, and conditions of the film for forming the case were adjusted as shown in table 2.

(example 16)

Next, the entire of the two opposing side surfaces, upper surface and lower surface of the laminate were wound with a 11 μm polyvinylidene chloride film, and a case-forming film having an average thickness of 100 μm was provided.

Thereafter, the laminate obtained in this manner in the state where the film for forming a case is provided is cut (cutting step), the sheet member obtained in the cutting step is pressed in the thickness direction thereof (pressing step), and further, the surface is polished with paper or a polishing tool (polishing step), whereby a thermally conductive sheet provided with a sheet main body provided with a thermally conductive portion and a joining portion and a case provided so as to be in contact with the outer periphery of the sheet main body is obtained (see fig. 8). In the cutting step, the angle formed by the stacking direction of the heat-conducting portion-forming sheets (the normal direction of the heat-conducting portion-forming sheets) and the cutting direction was adjusted to 19 °.

Comparative example 1

In this comparative example, the thermally conductive portion-forming sheet produced in example 1 above was used as a thermally conductive sheet as it is. That is, in the thermally conductive sheet of the present comparative example, the flaky graphite is oriented such that the thickness direction thereof is along the thickness direction of the thermally conductive sheet.

Comparative example 2

A thermally conductive sheet was produced in the same manner as in example 6, except that spherical graphite (graphite particles) was used instead of flake graphite in the production of the thermally conductive portion-forming sheet. The average particle diameter of the graphite particles was 20 μm.

The structures of the thermally conductive sheets of the above examples and comparative examples are shown in tables 1 and 2. In addition, each heat conduction portion and each joint portion are exposed on both main surfaces of each heat conduction sheet. In tables 1 and 2, the cured product of the SeRM Elastomer (manufactured by Advanced Soft Materials Co., Ltd.) is represented by "SeRM", and the cured product of the flexible phenol resin (manufactured by DIC Co., Ltd., J-325) is represented by "PH 3". In tables 1 and 2, the angle formed by the normal line of the heat conductive sheet and the normal line of the heat conductive portion is represented by θ 1, and the angle formed by the lamination direction and the cutting direction of the heat conductive portion forming sheet is represented by θ 2. The average flatness of the flaky graphite used in each of the above examples was 3 to 100 inclusive, and the average minor axis length was 0.2 to 50 μm inclusive. In the thermally conductive sheet of each of the above examples, the ratio of the flaky graphite in which the angle formed by the thickness direction (normal direction) of the flaky graphite and the y-axis direction is 10 ° or less among all the flaky graphite constituting the thermally conductive portion was 80% or more on a number basis.

[ Table 1]

[ Table 2]

(2) Evaluation of

First, the thermal conductivity of each of the thermally conductive sheets of examples 1 to 16 and comparative examples 1 to 2 was measured by a laser flash method. The results are shown in Table 3. When the thermal conductivity was measured by the laser flash method, LFA447 NanoFlash (a thermal conductivity measuring device manufactured by Netzsch corporation) was used.

[ Table 3]

Next, the cooling fin fixed to the CPU on the main board of a commercially available personal computer (FMVD 13002, manufactured by fuji corporation) via grease was removed, and the grease on the CPU was carefully wiped off. Next, the heat conductive sheet of the above embodiment 1 cut to its size is provided on the CPU, and the cooling sheet is re-fixed on the heat conductive sheet. Thereafter, the personal computer was started up in a room in which the temperature was controlled to 20 ℃, and the CPU temperature at the time of performing a predetermined process was measured by Speccy (manufactured by Piriform Ltd).

The same measurement was also performed on the thermally conductive sheets of examples 2 to 16 and comparative examples. In the measurement, the CPU temperature 30 minutes after the start of the predetermined process was evaluated based on the following criteria. It can be said that: the lower the CPU temperature is, the more excellent the thermal conductivity in the thickness direction of the thermally conductive sheet is.

A: the CPU temperature was less than 60 ℃.

B: the CPU temperature is 60 ℃ or higher and less than 65 ℃.

C: the CPU temperature is 65 ℃ or higher and less than 70 ℃.

D: the CPU temperature is 70 ℃ or higher and less than 75 ℃.

E: the CPU temperature is above 75 ℃.

The evaluation results of the thermally conductive sheets of examples 1 to 16 and comparative examples 1 to 2 are shown in table 4 below.

[ Table 4]

	Evaluation of
		Example 1	A
Example 2	B
		Example 3	A
Example 4	A
		Example 5	B
Example 6	A
		Example 7	A
Example 8	B
		Examples9	B
Example 10	B
		Example 11	A
Example 12	B
		Example 13	A
Example 14	A
		Example 15	A
Example 16	A
		Comparative example 1	E
Comparative example 2	D

As is clear from table 3, the thermally conductive sheet of the present embodiment is excellent in thermal conductivity in the thickness direction. The thermally conductive sheet of the present embodiment is excellent in flexibility and excellent in shape following property to the surface of a CPU as a high-temperature member. Further, when each of the heat conductive sheets for evaluation was removed from the personal computer and the appearance was observed, the heat conductive portions were prevented from buckling in the heat conductive sheets of examples 6 to 10 and 16, and the heat conductive portions and the joining portions were kept in close contact with each other in the entire heat conductive sheet. In addition, the thermally conductive sheet of the present embodiment can preferably produce a thermally conductive sheet having such excellent characteristics. In particular, in examples 11 to 16 using the case forming film, the laminate can be cut more easily. In contrast, the thermally conductive sheets of the respective comparative examples failed to obtain satisfactory results.

The same evaluation as that described above was performed using diamond grease instead of the heat conductive sheet, and as a result, the CPU temperature was 83 ℃.

Further, the thickness T10 of the heat-conducting portion is changed within a range of 50 μm to 300 μm, the thickness T20 of the joint portion is changed within a range of 0.1 μm to 200 μm, the content of the flaky graphite in the heat-conducting portion is changed within a range of 10 mass% to 90 mass%, the content of the resin fiber in the heat-conducting portion is changed within a range of 10 mass% to 90 mass%, the average length of the resin fiber is changed within a range of 1.5mm to 20mm, the average width of the resin fiber is changed within a range of 1.0 μm to 50 μm, the ratio (XG/Wt%) of the content XG [ mass% ] of the flaky graphite in the heat-conducting portion to the content XF [ mass% ] of the resin fiber is changed within a range of 0.10 to 9.0, a thermally conductive sheet was produced in the same manner as in the above examples and comparative examples, and evaluation was performed in the same manner as the above evaluation, except that the volume ratio of the thermally conductive portion to the entire thermally conductive sheet was changed to a range of 30 vol% or more and 90 vol% or less, the volume ratio of the bonding portion to the entire thermally conductive sheet was changed to a range of 10 vol% or more and 70 vol% or less, and the width W of the case was changed to a range of 30 μm or more and 1000 μm or less.

A heat conductive sheet was produced in the same manner as in the above examples and comparative examples, and evaluated in the same manner as in the above evaluation, and as a result, the same results as those described above were obtained.

(photograph of cross section of laminate)

Further, enlarged photographs of the cross section of the thermally conductive sheet of the above example are shown in fig. 20 to 23. In these drawings, fig. 20 shows a thermally conductive sheet of example 4, fig. 21 shows a thermally conductive sheet of example 1, fig. 22 shows an enlarged sectional view of a main portion of fig. 23, and fig. 23 shows an enlarged sectional view of a main portion of a thermally conductive sheet of example 1. The vertical direction in each drawing corresponds to the thickness direction of the thermally conductive sheet. Further, fig. 20 corresponds to a high-density product, and fig. 21 corresponds to a low-density product. As shown in fig. 22, it is judged that: in the high-density product, the thickness of the heat conduction portion 10 is about 65 μm, and a resin material is present as the joint portion 20 between the layered heat conduction portions 10. As described above, the joint portion 20 does not necessarily have to be present in a solid layer form, but is present in the form of a member partially or discretely joined by a resin material. In other words, the void layers are present at a relatively large ratio between the heat conduction portions 10. The gaps between the layered heat conduction portions 10 are partially formed in layers and exist as gaps between the layers. The presence of such a void layer improves the flexibility or pliability of the heat conductive sheet, and the heat conductive sheet can easily follow the shape or unevenness of the surface of the heating element HG or the heat sink in surface contact with the heat conductive sheet, and can be brought into close contact with these interfaces. Further, since the heat conductive portion 10 is also provided with the void portion, the flexibility of the heat conductive sheet is improved. On the other hand, by allowing the resin material to penetrate into a part of the void portion of the heat conductive portion 10, it is possible to secure strength for bonding the heat conductive portions 10 to each other while forming a void layer between the heat conductive portions 10.

The low-density product of fig. 23 shows a tendency that the void layer between the heat conductive portions 10 is larger. That is, a heat conductive sheet having a lighter weight and a higher deformability is obtained. In addition, since the joint portion 20 not only forms a void layer but also is partially joined by a resin material, the layered heat conductive sheet is maintained.

As described above, according to the thermally conductive sheet and the method for producing the thermally conductive sheet of the embodiment of the present invention, it is possible to provide a thermally conductive sheet excellent in thermal conductivity in the thickness direction and also excellent in flexibility.

Industrial applicability

In the heat conductive sheet and the method for producing the same of the present invention, the heat conductive sheet can be preferably used as a heat sink for electronic components such as a CPU, an MPU (Message Processing Unit), a GPU, and an SoC (system on chip) incorporated in a computer, and electronic components such as a light emitting element of an LED, a liquid crystal, a PDP (Plasma Display Panel), an EL, and a mobile phone. In addition, the buffer sheet can be preferably used as a buffer sheet interposed between a heat generating body such as a vehicle headlamp, a battery block used as a power source for an electric vehicle such as an electric vehicle or a hybrid vehicle, a semiconductor drive element, or an MCU (Micro Control Unit), and a heat sink.

Description of the symbols

1000 … heat sink

100. 200, 300 … heat conducting sheet

100' … tablet body

200 … sheet member

10 … Heat conducting portion

10' … heat-conducting-part-forming sheet

11 … graphite (flake graphite)

12 … resin fiber

20 … joint

20' … resin material

30 … casing

30' … film for forming case

40 … polyrotaxane

41 … Cyclic molecules

42 … first Polymer

43 … endcapping group

50 … second Polymer

60. 60B, 60C, 60D … laminate

HS … cooler

HG … heating element

T100 … thickness

T10 … thickness

T20 … thickness

Normal of N100 …

Normal of N10 …

Width of W …

RL1 and RL2 … wound body

RO2 … roller

BT … resin tank

CS … occlusion space

HT … heater

Claims

1. A heat conductive sheet is provided with:

a plurality of heat conduction portions provided continuously from one main surface to the other main surface, respectively; and

a joining portion that joins adjoining interfaces of the plurality of heat conduction portions stacked in the main surface direction to each other,

the heat-conducting fin is a sheet as a whole, and is characterized in that,

the heat-conducting portion includes a void portion,

the joint portion is made of a material containing a flexible resin material and is partially formed with a void layer,

a part of the resin material locally penetrates into the void portion of the heat conduction portion.

2. A thermally conductive sheet as claimed in claim 1,

0.2N/mm in the thickness direction of the thermally conductive sheet²When the thermally conductive sheet is pressed by surface pressure, the thermal conductivity in the thickness direction of the thermally conductive sheet is defined as lambda_0.20.8N/mm in the thickness direction of the thermally conductive sheet²When the thermally conductive sheet is pressed by surface pressure, the thermal conductivity in the thickness direction of the thermally conductive sheet is defined as lambda_0.8Wherein the unit of the thermal conductivity lambda is W/m.K, and in this case, lambda is 1.5. ltoreq. lambda_0.8/λ_0.2A relation less than or equal to 3.5.

3. A thermally conductive sheet as claimed in claim 1 or 2,

the ratio of the void layer in the joint is 2 vol% or more and 30 vol% or less.

4. A thermally conductive sheet according to any one of claims 1 to 3,

the heat conducting portion is made of a material containing graphite in a flake shape and a resin fiber.

5. A heat-conductive sheet as claimed in claim 4,

the resin fiber is aromatic polyamide fiber.

6. A thermally conductive sheet as claimed in claim 4 or 5,

the graphite is expanded graphite.

7. A thermally conductive sheet according to any one of claims 1 to 6,

the thermal conductivity of the thermally conductive sheet in the thickness direction measured on the main surface of the thermally conductive sheet by a laser flash method is 10W/m.K or more and 200W/m.K or less.

8. A thermally conductive sheet according to any one of claims 1 to 7,

the width of the heat-conducting portion in the in-plane direction of the heat-conducting sheet is 50 μm or more and 300 μm or less.

9. A thermally conductive sheet according to any one of claims 1 to 8,

the thickness of the heat-conducting sheet is more than 0.2mm and less than 5 mm.

10. A thermally conductive sheet according to any one of claims 1 to 9,

0.2N/mm in the thickness direction of the thermally conductive sheet²When the heat conductive sheet is pressed by the surface pressure of (2), the thickness of the heat conductive sheet is 0.1mm or more and 5m or lessm is less than or equal to m.

11. A thermally conductive sheet according to any one of claims 1 to 10,

the surface roughness Ra of the heat conducting sheet is more than 0.1 μm and less than 100 μm.

12. A thermally conductive sheet according to any one of claims 1 to 11,

the resin material includes: a polyrotaxane having a cyclic molecule, a first polymer, and a capping group; and a second polymer bonded to the polyrotaxane through the cyclic molecule, wherein the first polymer has a linear molecular structure and includes the cyclic molecule in a puncture-like manner, and the blocking groups are provided near both ends of the first polymer.

13. A thermally conductive sheet according to any one of claims 1 to 12,

an angle formed by a normal line of the heat-conducting sheet and a normal line of the heat-conducting portion is 25 ° or more and 90 ° or less.

14. A thermally conductive sheet according to any one of claims 1 to 13,

the interface between the heat conduction portion and the joint portion is formed in a curved surface shape.

15. A thermally conductive sheet according to any one of claims 1 to 14,

the heat-conducting portion and the joining portion laminated with each other are partially different in film thickness in the main surface direction of the heat-conducting sheet.

16. A method for manufacturing a thermally conductive sheet, which is a method for manufacturing a thermally conductive sheet having a plurality of thermally conductive portions stacked in a main surface direction, the plurality of thermally conductive portions being provided continuously from one main surface to the other main surface,

the method for manufacturing a thermally conductive sheet is characterized by comprising:

impregnating a heat-conductive-portion-forming sheet constituting a heat conductive portion with an uncured resin material;

a step of winding the heat-conductive-part-forming sheet impregnated with the uncured resin material into a roll shape;

curing the uncured resin material in the state of the wound roll; and

and cutting the cured wound body of the resin material in a plane perpendicular to, parallel to, or inclined to the axial direction of the roll shape.

17. The method for producing a thermally conductive sheet as claimed in claim 16,

before the step of impregnating the heat-conductive-part-forming sheet with an uncured resin material,

further comprising the step of preparing the heat-conducting portion-forming sheet in the form of a rolled roll.

18. The production method of a thermally conductive sheet as claimed in claim 16 or 17,

the uncured resin material is a thermosetting resin.